Diasporas and conflict

Diasporas and conflict Abstract We build a model of conflict in which two groups contest a resource and must decide on the optimal allocation of labor between fighting and productive activities. In this setting, a diaspora emanating from one of the two groups can get actively involved in conflict by transferring financial resources to its origin country. We find that the diaspora influences the war outcome and, above a certain size, contributes to the escalation of violence. Given the characteristics of the conflict equilibrium, the two groups of residents prefer to negotiate a peaceful settlement if there exists a sharing rule that makes both of them better off than war. We then identify the characteristics of the economy such that the diaspora acts as a peace-wrecking force or triggers a transition towards peace. Finally, we develop two extensions of the model, respectively, accounting for endogenous migration and the possibility of migration from both groups. Overall, our theory can help us make sense of several features of the interaction between real-world diasporas and conflict. 1. Introduction Poor countries are often plagued by civil wars and, in many cases, source of sizable migration flows. There is also abundant evidence that diasporas can play a major role in the evolution of conflict in the origin country, through various channels that range from political lobbying to financial support and direct involvement in fighting. In this article, we build a theoretical framework to understand how diasporas can affect conflict in the origin country, and act as a peace-building or peace-wrecking force. By doing this, we hope to fill a gap in the economic literature, which has so far overlooked the interaction between migrant groups and conflict in the homeland. The role of diasporas in conflict has instead attracted a lot of attention from political scientists. Horowitz (1985, 1998) emphasizes how, in the context of ethnic conflict, group members value group success per se, regardless of the individual benefits derived from victory. This consideration can easily be extended to migrants who maintain strong interests in conflict at home, and lies at the basis of a rich qualitative literature directly tackling the involvement of diasporas in homeland violence. Brinkerhoff (2011) provides a very interesting discussion of this literature and reviews the diverse modes of intervention that different diasporas have adopted. She emphasizes, in particular, the role of economic remittances (or financial contributions directly targeted towards armed groups and political parties), philanthropy, human capital support and political influence from abroad.1 Through all these means, diasporas can be at once conflict entrepreneurs, agents of competing interests and contributors to peace. This considerable heterogeneity in the role of diasporas in conflicts and post-conflict situations can be related, according to Van Hear and Cohen (2017), to multiple diaspora characteristics, such as location, resources and social capital. Overall, recent research in political science highlights the increasing importance of abroad-living communities as decisive transnational actors, which use various tools in order to influence the politics of the home country, eventually fostering violence or promoting conflict resolution (Roth, 2015).2 On the contrary, as mentioned above, the economic literature has remained so far quite silent on the role of diasporas in shaping conflict in the origin country. First, the vast literature considering the possible impact of emigration on sending countries’ outcomes has overlooked the onset and intensity of civil conflict as relevant variables of interest. Even the few papers interested in the consequences of migration for inter-group competition in the sending country (Docquier and Rapoport, 2003; Mariani, 2007) have not modeled conflict and the choice between war and peace. Some recent (and mostly empirical) studies, however, have shown that migrants can somehow shape institutions and politics in the sending country. For instance, Spilimbergo (2009) provides evidence that foreign students have a positive impact on democracy in the home country, while Docquier et al. (2016) emphasize a positive effect of emigration on institutional development in the sending country. Consistent with these cross-country results, a few micro-oriented papers document the impact of migration on political participation and opinions in the origin communities. In particular, Batista and Vicente (2011) find that Cape Verdean nonmigrants living in more migration-intensive localities exhibit higher demand for political accountability, Chauvet and Mercier (2014) show that Malian return migrants transfer electoral norms to their origin communities, notably in terms of participation, while Pfutze (2012) puts forward that migration increases the probability that an opposition party wins a municipal ballot in Mexico. Finally, in the case of Moldova, Barsbai et al. (2017) highlight the role of (return) migration in the transfer of preferences for democracy to the home country. Second, the otherwise rich literature on conflict tends to neglect the role played by diasporas. As far as empirical studies are concerned, the only exception has long been Collier and Hoeffler (2004), who highlight a positive correlation between the proportion of migrants in the USA and the probability of conflict in the home country, thus suggesting that diasporas may be a risk factor in the re-ignition of wars. More recently, Docquier et al. (2017) find that bilateral migration increases the likelihood of interstate conflict. As far as domestic conflicts are concerned, Preotu (2016) reports that emigration to developed countries can decrease the incidence of civil war in the countries of origin. What is still missing, however, is a proper theoretical framework to understand through which channels migrants influence the evolution of conflict in the origin country. As pointed out by Blattman and Miguel (2010), ‘an important limitation of the existing theoretical work on armed conflict causes [is] its almost exclusive focus on the internal armed groups’ decision of whether or not to fight’. This article is a first step in this direction, and thus contributes to the research agenda outlined by Constant and Zimmermann (2016). We present a model of conflict in which two groups contest a resource that can be consumed as a group-specific public good. Open conflict requires labor and involves some destruction of resources. Within each group, agents, who are ex ante identical, collectively decide on the optimal allocation of labor between direct participation to the conflict (as soldiers or activists) and productive activities. In this setting, we introduce a diaspora emanating from one of the two groups. In case of conflict, migrants can decide to provide funding to their group of origin (i.e. subsidize its war effort), thus affecting the intensity and outcome of conflict.3 Given the characteristics of the implied conflict equilibrium, the two groups of residents may choose to negotiate a peaceful settlement if there exists a sharing rule that makes both of them better off than war. Our analysis highlights the role that migration can play in the escalation of violence and resolution of conflict. Our contribution is threefold. First, we show that there exists a threshold diaspora size above which migrants provide a positive contribution to the war effort of their group of origin. This contribution increases with the size of the diaspora, leading in turn to an increase in the share of fighters in the origin group. Second, we also find that the peace—war tradeoff is affected by the diaspora, which can play either a peace-building or a peace-wrecking role. In particular, we show that it is more likely to act as a peace-building force in cases when negotiation is more costly, productivity is lower (which reduces the opportunity cost of violence) and/or the amount of contested resources is lower. Furthermore, we also show how the critical size that the diaspora needs to attain in order to trigger a switch from war to peace (and vice versa) depends on the size of the two resident groups. Such critical size notably turns out to be larger when the rival group is more numerous. Finally, the last part of the article extends our basic framework to two extensions: endogenous migration and multiple diasporas. In the first case, this allows us to highlight how migration costs interact with the group incentives for conflict to determine a peace-building or peace-wrecking equilibrium. The second extension uncovers the fact that diasporas act as strategic substitutes in terms of conflict activation or resolution: each diaspora attenuates the effect of the other, be it in a peace-building or peace-wrecking regime. The rest of the article is organized as follows. Section 2 describes a few case studies, which have received important attention from the political science literature and motivate our approach. The benchmark model is set up and solved in Section 3, and the results are interpreted in light of the previously cited case studies. Section 4 considers an extension of the benchmark model with endogenous migration, resulting from the strategic choice of the group of origin, while the possibility of multiple diasporas (i.e. migration from both groups), is dealt with in Section 5. Finally, Section 6 concludes and proposes some directions for future research. 2. Case studies The involvement of diasporas in homeland conflicts has been documented by qualitative research in different fields. Here we provide a (non-exhaustive) review of some well-known cases, in order to further motivate our analysis and highlight some characteristics of the peace-building or peace-wrecking role of migrant communities that our theory tries to make sense of. We will refer to these case studies when interpreting the main results of our model. 2.1. Sri Lanka One of the best known cases of conflict deeply shaped by the diaspora’s intervention is the Sri Lankan Civil War, which opposed the Tamil and the Sinhalese between 1983 and 2009. Starting from the early 1980s, Tamil migrants provided strong financial support to the main Tamil armed group in Sri Lanka, the Liberation Tigers of Tamil Eelam (LTTE). The diaspora, which relied on a well-organized global network to channel funds to the fighters on a very large scale, has been described by Joshi (1996) as the ‘economic backbone of the militant campaign’, and contributed significantly to sustaining the conflict.4 In addition to favoring the escalation of violence through massive financial support to its group of origin, the Tamil diaspora undertook a relentless lobbying activity aimed at mobilizing international opinion (Gunaratna, 2003; Fair, 2007; Orjuela, 2008). Eventually, however, at the end of the 1990 s, most of the main migrants’ host countries labeled the LTTE as a Foreign Terrorist Organization. In the aftermath of the 9/11 attacks, the suspicion over the funds sent by the Tamil migrant community became even stronger, leading to a change in the role of the diaspora, which started to support nonviolent conflict resolution and power-sharing settlements (Fair, 2007; Orjuela, 2008). 2.2. Ireland The Irish community in the USA is usually regarded as a decisive player for the evolution of conflict in Northern Ireland, and has been the object of a substantial amount of research in political science.5Cochrane (2007), among others, argues that Irish-American played a vital role in the decision of the Provisional IRA to terminate its paramilitary campaign in 2005. Over time, the Irish diaspora shifted from open support to armed struggle (with financial donations that helped IRA intensify its armed campaign) to a peace-building attitude based on soft power, as the objective of powerful civil society organizations gradually changed from a ‘united Ireland’ to a more process-oriented request of a well-balanced peace process.6 According to Cochrane (2007), this evolution in political views corresponded to (i) the transformation of Irish-American ‘from refugee/immigrant community to integrated, moneyed and highly networked sector of the indigenous population’, (ii) the demographic decline of the Irish diaspora, induced by smaller migration rates and (iii) the reduced tolerance of violence by the Irish-American and the higher cost of funding political groups abroad, in the aftermath of 9/11. While becoming more integrated in the American social fabric, the Irish diaspora also became less heavily concerned with the situation in Northern Ireland.7 2.3. Somalia Somali emigration probably displays more heterogeneity than other diasporas. First of all, as pointed out by Sheikh and Healy (2009), a first wave of essentially economic migration has been followed, in the 1990s, by conflict-driven migration. Second, the Somali diaspora is made up of different sub-diasporas, each one with a different reference group (or clan) in the home country. Third, the diaspora has contributed to both peace-wrecking and peace-building efforts, in different times and regions. Until the early 1990s, Somalis in the diaspora were strongly pressured by local clan representatives to support the fighting effort of their group of origin, thus acting as fundraisers for clans militias. The decision of Somali migrants to finance conflict, as noticed by Mohamoud (2006), may also have resulted from (i) opportunistic motivation, with diaspora members donating funds to faction leaders and militia in the hope of obtaining power and government positions at the issue of conflict and (ii) disillusionment and frustration about the failure of ongoing peace negotiations. Along with this essentially peace-wrecking (or conflict-perpetuation) role, members of the Somali diaspora—especially more recent migrants, and in specific regions such as Somaliland—have also acted as promoters of peace, good governance and development and have undertaken peace-building initiatives, which have played an important and effective role.8 As far as the diaspora’s means of intervention are concerned, remittances at the clan level have been used not only to sustain war, but also to finance compensational payments (diya) deemed necessary for the reconciliation process between clans. Horst (2008) also highlights how diaspora remittances used to buy arms may have produced peace-building effects, by deterring violence from other groups. 2.4. Croatia Skrbiš (2000) emphasizes that financial participation was nearly mandatory for Croatian migrants, with diaspora resources being used both for fighting in the home country and campaigning in the host countries to seek support and recognition of the new state. Before the ascent of the Croatian Democratic Union (HDZ), the Croatian diaspora, which was already constituted as pro-independence by the time of Tito’s death in 1980, lacked a corresponding movement in the homeland and was unsuccessful in fueling conflict. Yet, during the escalatory phase of the conflict (1987–1991), Croatian emigrants largely intervened in the war for independence by providing strong financial assistance to Tudjman’s HDZ, which led the secession from Yugoslavia. Most diaspora funds were used to finance the political activities of the opposition, with whom the diaspora shared its willingness to oust the communist government and take concrete steps towards independence.9 2.5. Cuba Last, the Cuban case provides an interesting example of a diaspora whose attempts to ignite war in the origin country failed. After the revolution of 1959, important waves of emigrants fled the communist regime and settled down in the USA. Since then, the Cuban diaspora has been dominated organizationally by early migrants, who identified with the overthrown Batista dictatorship and remained strongly hostile to the revolutionary leaders. Although de facto unsuccessful at overthrowing Castro, the diaspora, through relentless lobbying activity, managed to keep Cuba at the top of the US foreign policy agenda and strongly affected the ability of the political regime in the homeland to carry on. In this respect, it can be noticed that whereas the dominant factions in the Cuban diaspora in the USA have maintained a highly conflictual approach to Castro’s Cuba, there are indications that younger generations, characterized by a more diverse and post-Cold War culture, are more supportive of a more pragmatic approach and would welcome a negotiated transition to democracy (Grugel and Kippin, 2007). 2.6. Further examples Beyene (2015) compares the roles of diasporas from Kenya, Nigeria and Ethiopia, which are known to send huge amounts of remittances to their (often conflict-plagued) home countries. He points out that the well-organized Kenyan diaspora is primarily involved in conflict resolution and peace-building affairs.10 On the opposite, migration from Ethiopia, mostly conflict-generated and in strong opposition with the government, appears to have had a peace-wrecking role and participated to the escalation of conflict.11 Somewhere between these two polar cases, the vast majority of Nigerian diaspora seems relatively inactive in conflict and political affairs in Nigeria. Other notable examples of migrants’ involvement in homeland conflict include communities as diverse and complex as the Armenian, Jewish, Kurdish, Albanian, Colombian or Cambodian diasporas. Overall, such cases are also extensively documented by an important literature in political sciences (see in particular Smith and Stares (2007), Roth (2015), Shain (2002), Pirkkalainen and Abdile (2009) and Koinova (2011)), and reproduce some of the features discussed in this section, thus adding up to the motivation of our research. 3. The model We start by presenting a simple model of conflict involving two rival groups. We are agnostic with respect to the source of difference between the two groups, which can be ethnic, religious, political, etc. As far as the benchmark version of the model is concerned, migration is assumed to be exogenous, and related to one group only. 3.1. The economic environment Total population is divided into two groups, indexed by E (the ‘elite’) and O (the ‘other’ group), respectively.12 Group E is made up of εE individuals, all residing in the homeland and characterized by productivity yE. Group O is originally made up of εO individuals. However, m members of this group migrate and live abroad. The εO – m resident members of group O have productivity yO, while the m migrants (who will be henceforth referred to as group M) are characterized by a productivity (1+μ)yO, with μ a strictly positive migration productivity premium. We further assume yE = κ yO = κy, with κ > 0, so that y can be interpreted as the overall level of development of the economy while κ is a measure of between-group inequality. In order to sidestep external effects and free-riding problems, we assume that each group’s decisions are taken by a leader who aims at maximizing the group’s average utility. As in Esteban and Ray (2008, 2011), individual utility is derived from private consumption c, and from a group-level public good Q which depends on the appropriation of a given resource (or public budget) R. The average utility functions maximized by the three group leaders are given by   uE=cE+χQE, (1)  uO=cO+χQO, (2) and   uM=cM+ηχQO, (3) where χ > 0 denotes the preference for the public good, which is further weighted by η > 0 in the case of migrants. Hereby we are suggesting that migrants are interested in the access of their group of origin to the public good, but may attach to it a different weight in their utility function.13 The quantity Qi (i = E, O) of public good that groups O and E can have access to depends on the appropriation of a contested resource R. Examples may range from the obtention of a (share of the) public budget highlighted by Esteban and Ray (2008, 2011), to sheer territorial expansion. The contested resource may be subject to violent conflict or shared through a process of negotiation. In case of conflict, group E (respectively, O) obtains a share s (respectively, 1 – s) of R, where s is given by the following contest function:   s(AE,AO)=γAEγAE+(1−γ)AO. (4) In the above expression, Ai (i = E, O) denotes the number of soldiers (or activists) that group i allocates to conflict and γ represents the relative (dis)advantage of group E in conflict.14 It reflects the idea that, prior to conflict, the two groups may have a different access to conflict-related information or technology, for instance.15 Alternatively, s(AE, AO) can be interpreted as the probability that group E will capture the whole amount of resource R. Open conflict is costly: it entrains the destruction of a share δ of the total resources located or produced in the economy, that is, residents’ private production (yO and yE) and R. Migrants differ from residents for they are not concerned by the destructive effect of war on private production. Conflict has also an opportunity cost: those who are employed as soldiers are removed from productive activities so that, for instance, group O gives up a total quantity of private consumption equal to AOcO. Such opportunity cost, however, cannot be directly affected by migration as long as we assume a constant marginal productivity of labor. Removing this assumption, in favor of decreasing marginal productivity, would imply that emigration, by reducing the size of the origin group, increases the wage of its members and, concomitantly, the opportunity cost of fighting. In this context, migrants can decide to get actively involved in the conflict by subsidizing soldiers from their group of origin (O).16 The value of the subsidy and the very fact that migration makes group O shrink are the two channels through which the diaspora interplays with conflict and the peace–war choice in our model. We rule out, however, that migrants can be recruited as soldiers, as well as the possible productivity and price effects of migration on the home economy.17 In case the two groups choose to split resources without resorting to armed conflict, they engage in a process of negotiation and must ultimately agree on the sharing rule s. Negotiation imposes a cost Z onto each group. Such a cost is justified by negotiation being time- or resource-consuming, and also accounts for the possibility that past conflicts generate hatred and distrust between the involved actors, thus making them, to some extent, prefer war over pacific settlement. A positive Z may also be related to the lack of a perfect commitment technology associated with the peaceful settlement of the conflict. 3.2. The model with conflict 3.2.1. Optimal choices Suppose now that R is contested through violent conflict. The leaders of the two resident groups E and O must determine the share of the labor force that they allocate to conflict, choosing θE and θO such that AE = θEεE and AO = θO(εO – m), respectively. On the other hand, the leader of group M decides a, that is, how much the diaspora will contribute for each soldier deployed by group O. This transfer may thus be interpreted as a subsidy to group O’s involvement in conflict. The total amount of war-targeted financial transfers, aAO, will then be shared equally among the resident members of group O, thus reducing the opportunity cost of war for group O. In our framework, production in the origin country is entirely transformed into private consumption. Accordingly, in case of war uE and uO write as   uE,w=(1−δ)((1−θE)κy+χs(AE,AO)R), (5) and   uO,w=(1−δ)((1−θO)y+aθO+χ(1−s(AE,AO))R), (6) respectively. Given that the utility function is linear in its two arguments, the convexity of the problem derives from the shape of the contest function. For a given a, the first order conditions ∂uE,w/∂θE=0 and ∂uO,w/∂θO=0 yield the reaction functions of the two groups, that is,   θE(θO)=γεE(1−γ)(εO−m)κyθOχR−κy(1−γ)(εO−m)θOκyγεE, (7) and   θO(θE)=γεE(1−γ)(εO−m)(y−a)θEχR−(y−a)γεEθE(y−a)(1−γ)(εO−m). (8) Figure 1 depicts the two reaction functions, as well as their intersection, which corresponds to the following equilibrium values:   θE*(a)=χR(1−γ)(εO−m)γεE(y−a)((y−a)γεE+κy(1−γ)(εO−m))2, (9)  θO*(a)=χR(1−γ)(εO−m)γεEκy((y−a)γεE+κy(1−γ)(εO−m))2. (10) Figure 1 View largeDownload slide Reaction functions of groups E and O. Figure 1 View largeDownload slide Reaction functions of groups E and O. The best-response functions are hump-shaped, meaning that when a group is faced with increasing opposition it initially responds by escalating conflict, but it is eventually limited by its resource constraint and decreases its involvement in conflict if the other group’s activism grows further. In case of complete symmetry ex ante and in the absence of active intervention by the diaspora (γ = 1/2, κ = 1, εE = εO – m, a = 0), the conflict equilibrium is also symmetric and lies on the 45° line. From θE*(a) and θO*(a) we can obtain AE*(a) and AO*(a), that is, the equilibrium sizes of the two armies, depending on a. As far as the diaspora is concerned, uM can be written, in case of conflict, as   uM,w=(1+μ)y−aθO*(a)(εO−m)m+(1−δ)ηχ(1−s(AE*(a),AO*(a)))R. (11) Knowing θE*(a), θO*(a), AE*(a) and AO*(a), the leader of group M maximizes uM,w with respect to a, the amount transferred to each soldier of group O. From ∂uM,w/∂a=0, we can retrieve a* as a function of m. It is possible to show that there exist m1 and m2 such that:   a*={0if m≤m1y(γεE+(1−γ)κ(εO−m))((1−δ)ηm−(εO−m))γεE((1−δ)ηm+(εO−m))if m1<m<m2y(γεE+(1−γ)κ(εO−m))−γεE(1−γ)(εO−m)κyχRγεEif m2≤m<εO. (12) If 0 < m ≤ m1, the optimization program of group M would lead to negative values for a*. Since the diaspora can only provide a non-negative contribution, we consider 0≤m≤m1 to be associated with the corner solution a* = 0.18 When m reaches m1, the diaspora becomes big enough for a strictly positive involvement in the conflict to be optimal. The size of this contribution increases with the number of migrants m.19 Finally, when m equals m2, the contribution of the diaspora is large enough to make θO reach one. In other words, group O’s involvement in conflict is so heavily subsidized by emigrants that all the resident members of group O are employed as soldiers (or activists), and payed out of the diaspora’s contribution. Overall, the function a*(m) behaves as represented in Figure 2. Figure 2 View largeDownload slide Equilibrium response of group M. Figure 2 View largeDownload slide Equilibrium response of group M. 3.2.2. Equilibrium We now turn to the analysis of the conflict equilibrium. By using the expression for a* in Equation (12) to replace a in Equations (9) and (10), we obtain the equilibrium values θE*, θO* and a* as functions of the parameters only. In order to have shorter expressions, we impose a few restrictions on the parameters. In particular, we set γ = 1/2 (symmetry in conflict between groups E and O), κ = 1 (groups O and E have the same productivity) and η = 1 (migrants value the public good as much as residents). We also assume that the parameters satisfy the following: Assumption 1 1−δ2<εEεO<1−δδ. This assumption, which is by no means necessary for the model to be solved but allows us to derive simpler results, requires the two groups not to be too different in size, so that none of them is big enough to push the other group out of conflict if its size marginally increases. Note also that the model can be fully solved in the general case of 0 < γ < 1, κ > 0 and η > 0 and would yield qualitatively similar results. Once the above assumption and parameter restrictions are taken into account, we can rewrite Equation (12) as:   a*(m)={0if m≤m1y(εE+(εO−m))((2−δ)m−εO)εE(εO−δm)if m1<m<m2y(εE+(εO−m))−εE(εO−m)yχRεEif m2≤m<εO (13) where   m1=εO2−δ, (14) while m2 solves θO*(a,m)=1.20 Although a* depends on several parameters, we use the notation a*(m) (as well as θE*(m) and θE*(m)) in order to highlight the impact of the diaspora size on the conflict equilibrium. By replacing a*(m) in θE*(a) and θO*(a), we further obtain:   θE*(m)={(εO−m)εEy(εE+(εO−m))2χRif m≤m1(εO−δm)(2εE+εO−m(2−δ))4y(εE+(εO−m))2χRif m1<m<m2εE(εO−m)yχR−yεE(εO−m)yεEif m2≤m<εO, (15) and   θO*(m)={(εO−m)εEy(εE+(εO−m))2χRif 0<m≤m1(εO+δm)2εE4y(εO−m)(εE+(εO−m))2χRif m1<m<m21if m2≤m<εO. (16) For ease of exposition, we call A, B and C the three regions defined by m≤m1, m1<m<m2 and m≥m2, respectively. The relationship between the diaspora’s contribution to conflict a* and its size m, for all admissible values of m, can be described as follows. Proposition 1 The value of the diaspora’s contribution at equilibrium, a*(m), is zero over region A. It is an increasing function of m over region B and a U-shaped function of m over region C.Proof. Follows from the inspection of the partial derivatives of the expression of a*(m) given by Equation (13). ▪ Looking at m1, we first can see that the minimal size at which the diaspora starts intervening actively in the conflict increases with εO and δ. If migrants come from a relatively small origin group, the size of the diaspora such that they start subsidizing conflict in the home country is also small. On the other hand, when a conflict is potentially more destructive (all other things being equal), the diaspora needs to reach a larger size before being interested in getting actively involved in the conflict. When the size of the diaspora is smaller than m1, there is no contribution from migrants. When m1 < m < m2, the diaspora intervenes actively in the conflict, and its contribution increases with its size. Finally, when m exceeds m2, the contribution of the diaspora ensures that θO remains constant and equal to 1.21 The following Proposition describes how the shares of workforce that, in equilibrium, the two groups allocate to conflict, depend on the size of the diaspora. Proposition 2 The relationship between the size of the diaspora and the shares of soldiers in each group depends on the shape of the diaspora’s contribution. In particular, over region A, θO*and θE*are ∩-shaped functions of m; over region B, θO*is a growing function of m while θE*is ∩-shaped; over region C, θO*is constant and θE*is a ∩-shaped function of m. Proof. Follows from the inspection of the partial derivatives of θE*(m) and θO*(m) as in Equations (15) and (16) with respect to m. ▪ Over region A, that is, as long as the diaspora does not subsidize conflict, groups O and E behave symmetrically and allocate the same share of their labor force to conflict. Each group’s θ* increases with the group’s size, as long as the latter is smaller than the other group’s size. However, if an already dominant group grows even bigger, both groups allocate a smaller share of their human resources to fighting. Within this region, although the diaspora does not contribute to the conflict, it influences it by its size. Namely, the share of soldiers in each group is a ∩-shaped function of m: when the number of migrants gets larger, group O becomes automatically weaker than group E in case of conflict, and must compensate by increasing its military engagement. Group E will react accordingly by increasing θE*. Eventually, however, if the diaspora grows further the pool of available soldiers becomes too small for group O to be able to prevail: group O will then withdraw human resources from conflict, causing group E to do the same. Within region B, the diaspora’s financial support to group O is internalized by both groups in their decision over the optimal share of soldiers. Different from region A (corner solution with ‘passive’ diaspora), the two groups do not have symmetric behaviors. In particular, the share of soldiers in group O always increases with the size of the diaspora. On the other hand, the impact of the diaspora’s support on θE*(m) is of ambiguous sign: it is positive when εE>(1−δ)m and negative when the inequality is reversed. When the diaspora is relatively small (with respect to group E), its financial involvement in conflict does not represent too big a threat for group E, which will simply adjust its θE* to match a larger a* and the implied increase in θO*. When the number of migrants is relatively large, the diaspora’s contribution to group O may act as a deterrent for group E, which prefers to reduce the number of its soldiers. Last, when m exceeds m2 (region C), the money sent back home by the diaspora is such that θO*=1. This region corresponds to another corner solution, in which the diaspora is active but, eventually, only affects the equilibrium via size effects since θO* is constant. Although interesting, the corner regions A and C are less informative regarding the interactions between diaspora and conflict. Within region A, the diaspora does not contribute financially to the conflict and only plays a role through a mechanical size effect. Region C sees group O invest all its human resources in conflict, regardless of the size of the diaspora. In what follows, we thus assume that the following holds. Assumption 2. The size of the diaspora is such that m1 < m < m2. This means that we focus on region B, where we observe simultaneously the size effect and the contribution effect of the diaspora. 3.3. War versus peace So far we have analyzed a situation of conflict, in which the two groups resort to war in order to ‘conquer’ their shares of the contestable resource R. However, this is not the only option available to the leaders of the two groups, who can alternatively sit at a table and peacefully negotiate how to share R. Negotiation implies that both parts agree on a sharing rule s, such that group E obtains fraction s of R, while fraction 1 – s goes to group O. Given the conflict-equilibrium value θi*(m) (i = E, O), the leader of group i may prefer to engage in a negotiation, which implies a fixed cost, rather than initiating conflict, which destroys resources and requires labor force. For this to be the case, there must exist a non-empty set of values of s such that the utility of group i in case of war, ui,w, is lower than its utility if a peaceful settlement is reached, ui,p. For negotiation to actually take place, there must exist values of s such that both groups are better off without war. Replacing a*, θE* and θO* into Equations (5) and (6), the utilities of the two groups in case of conflict can be rewritten as:   uE,w(m)=(1−δ)(y+(2εE+ε0−m(2−δ))2χR4(εE+(εO−m))2), (17) and   uO,w(m)=(1−δ)(y+(εO−δm)2χR4(εE+(εO−m))2). (18) Peaceful settlement avoids the destruction generated by conflict, and keeps all the labor force in the productive sector (θO and θE are set to zero). However, it implies that both groups pay a fixed cost Z. In case of peace, groups E and O thus obtain   uE,p=y+sχR−Z (19) and   uO,p=y+(1−s)χR−Z, (20) which, different from uE,w and uO,w do not depend on m. Solving ui,p = ui,w (for i = E, O), we can determine the threshold functions s˜E(m) and s˜O(m). These functions give the values of s which, for each possible m, make the two groups indifferent between open conflict and peaceful settlement. In particular, we obtain   s˜E(m)=Z−δyχR+(1−δ)((2εE+ε0−m(2−δ))24(εE+(εO−m))2), (21) and   s˜O(m)=1−(Z−δyχR+(1−δ)((εO−δm)24(εE+(εO−m))2)). (22) The two groups agree on a peaceful negotiation only if there exists a sharing rule s which makes both of them better off than war. It then follows that Proposition 3 For any given m, a pacific settlement is viable only if s˜E(m)≤s˜O(m). The negotiated sharing rule s is a priori undetermined, as there exist multiple values of s such that the two groups prefer peace to war. To resolve indeterminacy, we will assume later on (see Section 3.4) that in case of peace the sharing rule is the outcome of a Nash-bargaining process. Under Assumption 2, both functions s˜E(m) and s˜O(m) are decreasing with m. By subsidizing group O in case of conflict, a larger diaspora induces a higher propensity for group O to engage in conflict, while strengthening the preference of group E for a peaceful settlement. Otherwise said, a larger m strengthens the bargaining power of group O by increasing its conflict outcome uO,w. To assess whether the groups actually choose to negotiate peace, depending on m, we need to establish under which conditions s˜E(m) is smaller than s˜O(m). In case s˜E(m)>s˜O(m), no peaceful sharing rule would make both groups better off than war, which will then be the equilibrium. Switches between war and peace occur for values of m such that s˜E(m)=s˜O(m). Proposition 4 Let m^ and m¯ be the two values of m that solve s˜E(m)=s˜O(m), with m^<m¯. Under Assumption 2 (i.e. the diaspora’s contribution is positive but not large enough to push group O to employ all its members as soldiers), there exist   Z0=δy+14(1+δ)χR and   Z1=δy+χR(δ2+(2−δ)(1−δ)2εEεO((2−δ)εE+(1−δ)εO)2),with Z0 > Z1, such that: If Z > Z0, the diaspora cannot prevent war in the home country, that is, s˜E(m)>s˜O(m). If Z1 < Z < Z0, the two groups are at war for m = m1 and the diaspora is potentially peace-building. A switch from war to peace occurs within region B if m^<m2. A second switch from peace to war may also exist if m¯<m2. In such a case, an initially peace-building diaspora turns peace-wrecking as it becomes very large. If Z < Z1, the two groups are at peace for m = m1 and the diaspora is potentially peace-wrecking. A switch from peace to war occurs within region B if m¯<m2.Proof. Solving s˜E(m)=s˜O(m) yields the two possible solutions m^ and m¯, whose expressions are given in Appendix A. These solutions are real numbers only if Z < Z0. If Z > Z0, the two curves s˜E(m) and s˜O(m) do not cross, and s˜E(0)>s˜O(0). This proves (i). If Z < Z0, the two curves s˜E(m) and s˜O(m) intersect twice over ]−∞,∞[. Whether the two intersections m^ and m¯ fall within ]m1,m2[ determines possible switches from war to peace and peace to war. We also know that s˜E(m) and s˜O(m) are both decreasing functions of m over ]m1,m2[, but that there exists a value of m larger than m2 above which s˜E(m) starts increasing with m. This implies that m^ corresponds to a switch from war to peace, and that m¯ corresponds to a switch from peace to war. If Z1 < Z < Z0, m^>m1. This implies that s˜E(m1)>s˜O(m1) and the two groups are initially (i.e. at m = m1) at war. As soon as m reaches m^, s˜E(m) becomes smaller than s˜O(m) and the two groups prefer to peacefully share the contested resource. Peaceful negotiation effectively happens if m^ falls within the boundaries of region B, that is if m^<m2, and the diaspora then has a peace-building effect. Last, if m¯ also falls within the boundaries of region B ( m¯<m2), the diaspora can trigger a second switch from peace to war for large values of m. This proves (ii). Finally, if instead Z < Z1, then m^<m1 and the two groups are at peace when m = m1. However, if m¯ falls within region B, a growing diaspora is able to trigger a switch from peace to war, which proves (iii). ▪ Figures 3–5 describe the possible cases of non-neutral diaspora (i.e. when Z < Z0). The red (respectively, blue) line represents the threshold value of the sharing rule above (below) which group O (E) does not accept peaceful settlement. These lines are dashed in case of war, when the sharing rule derived from the conflict equilibrium is represented by the purple line. They are instead solid when the equilibrium is peaceful, that is, when s˜E(m)<s˜O(m), with the light green area representing the set of feasible sharing rules. Within this area, the solid green line depicts, for every possible m, the negotiated sharing rule derived from the Nash-bargaining process. Figure 3 View largeDownload slide Peace-building diaspora. Figure 3 View largeDownload slide Peace-building diaspora. Figure 4 View largeDownload slide Peace-building, then peace-wrecking diaspora. Figure 4 View largeDownload slide Peace-building, then peace-wrecking diaspora. Figure 5 View largeDownload slide Peace-wrecking diaspora. Figure 5 View largeDownload slide Peace-wrecking diaspora. In all cases, when m≤m1 (region A), s˜E(m) and s˜O(m) are both increasing with m. The diaspora does not contribute and only has a size effect on the equilibrium, making group E (O) more (less) willing to engage in conflict. Figure 3 describes the case of a peace-building diaspora (Z1 < Z < Z0). The two groups are at war when m = m1, and when m reaches m^, the diaspora is sufficiently large to trigger a switch to peace. Eventually, if m¯ is within region B, peace can be broken again when migration reaches this second threshold value. The diaspora then first plays as a peace-building actor, but turns peace-wrecking if its size becomes very large. Figure 4 illustrates this specific case. Last, Figure 5 describes the case of a peace-wrecking diaspora. The two groups are at peace when m = m1, which necessarily implies m^<m1<m¯. Peace prevails for every m smaller than m¯. When m eventually reaches m¯, the diaspora triggers a switch from peace to conflict. As stated by Proposition 4, the diaspora is neutral when the cost of peace is too high (Z > Z0), it has a peace-building potential when the cost of peace is relatively, but not prohibitively, high (Z1 < Z < Z0), and a peace-wrecking potential when the cost of peace is low (Z < Z1). In particular, a situation in which the diaspora, regardless of its size, has no chance whatsoever to pull the origin country out of war is more likely when Z0 is small. This corresponds to a relatively low cost of the war (low δy and/or low δχR). On the contrary, when the cost of the war is high (Z0 large), the diaspora is more likely to be able to play a role. If the diaspora is non-neutral (Z < Z0), it is more likely to play a peace-building role if Z1 is small. Looking at the effects of the parameters on Z1, the peace-building scenario becomes more likely if y, χ and R decrease. In fact, if a switching point exists, it will be from war to peace if s˜E(m1)>s˜O(m1), that is, the economy is at war when m = m1. This is more likely when the resources subject to potential destruction (y, R) as well as the importance of the contested resource in the utility function (χ) are limited. Finally, it may be interesting to look at the effect of the parameters on m^ and m¯, that is, the threshold size that the diaspora must reach in order to bring about a switch from war to peace and vice versa. The comparative statics on m^ and m¯ are not obvious because in general, they depend on specific conditions on the parameters. We can however prove the following results concerning the effects of the two groups’ size. Proposition 5 The threshold values m^ and m¯ increase with εE. They also increase with εO if εE < (1 – δ)m.Proof. The results can be established by applying the Implicit Function Theorem, under Assumption 1. ▪ The first result tells us that, as expected, it takes a larger diaspora to make the difference when the size of group E increases. In addition, the thresholds values increase with the size of group O only when group E is relatively small. This is due to the fact that the marginal impact of the diaspora on the origin group’s outcome decreases with the size of group E.22 3.4. Nash bargaining As mentioned above, if groups E and O decide to avoid war and resort to peaceful negotiation in order to split R, there can exist a set of values of s they may agree upon. To resolve such indeterminacy, we assume that the value of s which emerges is the outcome of Nash bargaining, that is   s(m)=arg max s(uO,p−uO,w(m))(uE,p−uE,w(m)). (23) In other words, the two groups maximize the product of their respective surpluses from peace (defined using war utilities as ‘threat points’).23 In particular, after replacing the conflict-equilibrium values θE*, θO* and a* in the utility functions, we obtain   s(m)={δ2+(1−δ)εEεE+εO−mif 0<m≤m1(2−δ)εE+εO−m(2−(2−δ)δ)2(εE+εO−m)if m1<m<m21−δ2−(1−δ)y(εO−m)y(εO−m)εEχRif m2≤m<εO. (24) It can be shown that the negotiated s is always increasing in m over regions A and C, while it decreases with m over region B under Assumption 1. This is due to the effect of m on the war outcomes of the two groups. As long as the diaspora does not subsidize conflict (region A), a larger m imposes a negative size effect on the share of resources that group O can obtain in case of war, thus weakening its bargaining power and leading to a higher s. A similar situation occurs in region C, where θO*=1: as group O shrinks, due to increased migration, its war outcome worsens and the share 1 – s of resources it can obtain through negotiation decreases. Instead, within region B, a larger diaspora translates into a potentially higher war outcome for group O, which can thus negotiate peace on better terms and impose a lower s on group E. 3.5. Back to the case studies Here, we try to bring back the results of our model to the case studies presented in Section 2. In particular, we argue that some of our theoretical findings are consistent with, and can be used to explain some distinctive features of the interaction of real-world diasporas with conflict in the origin country. In the case of Sri Lanka, we have seen that the political science literature emphasizes a major change in the attitude of the Tamil diaspora: in the aftermath of 9/11, with mounting international suspicion over the LTTE’s activity, diaspora members took some distance from their group of origin in the home country, loosened the links within their transnational networks, and increasingly supported a peaceful settlement. In the framework of the model, the evolution of the international environment can be thought of—from the viewpoint of the migrants’ group M—as an exogenous increase in the cost of subsidizing the war effort of group O. As a consequence, a*(m) becomes lower, thus contributing to the de-escalation of violence at home through a smaller θO*(m). An alternative interpretation would be that the increasing international attention on the transnational financing of armed groups implies a lower cost of peace (smaller Z), which in turn makes the diaspora less likely to fulfill its peace-wrecking potential.24 As far as the conflict in Northern Ireland is concerned, the involvement of the Irish-American community has undergone a clear evolution, from a strong support of armed struggle to a decisive peace-building role. Such evolution is traditionally explained with the transformation of the Irish-American community itself, which (i) evolved from a group of poor refugees and immigrants into a moneyed and highly networked community, well integrated in the American society, (ii) had its size eroded by demographic factors, namely smaller migration rates and (iii) became less tolerant of violence (and encountered more difficulties in funding political groups in Ireland) in the aftermath of 9/11. Our model can account for each of these mechanisms. In fact, a weaker adherence to the objective of the origin group (lower χ), a shrinking of the diaspora (lower m) driven by socio-demographic factors, and a lower cost of peace (lower Z) are all factors that can prevent a potentially peace-wrecking diaspora from igniting conflict at home. Also in the case of Somalia, our model can make sense of some specific features of the diaspora’s participation to conflict in the homeland. In particular, Somali migrants in different times—or different migrant groups—are known to have financed conflict in the home country in the hope of obtaining future benefits, and somehow gave up with the peace-building process since they had different stakes in conflict than the community of origin (which justifies the role and the consequences of χ and R in our model). The Somali case also provides a good justification for introducing a cost of peace Z, as modeled in Section 3. In fact, the peace-building effort of the diaspora was at times based on their willingness to finance compensational payments between fighting groups. Furthermore, we know from Section 2 that peace-wrecking diaspora remittances, which were intended to finance conflict and buy arms for the origin group, may have instead produced a peace-keeping effect by deterring violence from competing groups. This is fully consistent with our basic model (namely Section 3.3), where an arms race—possibly financed by migrants—prevents the outburst of conflict. Finally, the fact that Somali migrants were almost forced by clan leaders to finance the war effort of their origin groups provides some motivation for the extension presented in Appendix B, where we assume that the leader of group O controls the financial contribution of migrants.25 In a similar way, the presence of migrants from different groups in conflict in the Somali diaspora (and its consequent inability in determining the outcome of conflict in the home country) is captured by our extension with multiple sub-diasporas, developed in Section 5. Let us also stress that the presence of a large wave of pre-war, economic migration from Somalia, which played a substantial role in escalating conflict, somehow lends credibility to our benchmark setting with exogenous migration. The Croatian diaspora, which had peace-wrecking ‘intentions’, was initially unable to ignite a war for independence, essentially because it lacked local support in the homeland, but eventually became more effective during the second half of the 1980s. Our model suggests two possible explanations that are also compatible with historical evidence. First, the ascension of Milosevic to power in Serbia in 1987 led to a dramatic rise of nationalism. In our framework, this can be proxied by an increase in χ (the weight attached to the contested resource or public budget), which, as can be seen from Equations (15) and (16), translates into a higher intensity of conflict. Second, the substantial increase in Croatian migration during the 1980s may have helped the diaspora to bring about the transition towards war, which corresponds to a raise in m in Figure 5.26 Last, the case of Cuba, whose diaspora never managed to suscitate a counterrevolution in the homeland, can be interpreted, in terms of our model, as the diaspora failing to reach the threshold m¯ above which its involvement could have endangered peace (Figure 5). Recalling that this threshold depends positively on εE and negatively on εO as soon as εE is large (Proposition 5), it can be argued that the support that Castro had at home (large group E) or, alternatively, the virtually non-existent opposition inside the island while most of the opposition was abroad-living, prevented the diaspora from being actually peace-wrecking.27 4. Endogenous migration The model developed in Section 3 considers migration as exogenous. It may be argued, however, that migratory flows are not orthogonal to the existence of (a latent) conflict, and could result from the strategic choices of the two groups. To deal with this issue, we develop in this Section an extension of the benchmark model in which the leader of group O also chooses m so as to maximize the payoff of her group, taking into account that the resulting diaspora behaves as described by Section 3. This means that, although m is chosen by the leader of group O, the diaspora’s involvement in conflict, a, is decided by the leader of group M: once migrants are abroad, the leader of group O does not control their behavior anymore. In Appendix B, we will explore an alternative setting, in which the leader of group O controls both m and the possible transfers of resources between the diaspora and the homeland. In particular, the leader of group O chooses optimally both m and θO, taking into account that emigrants cannot become soldiers, and then equalizes utility across all group members, be they at home or abroad, by eventually transferring funds from the diaspora to the origin country. In this setting, the diaspora may thus be ‘forced’ to subsidize its origin’s group participation to conflict.28 4.1. The extended model: setup With respect to Section 3, we introduce two main changes. First, the objective function of the leader of group O modifies into   UO=εO−mεO(uO−Cm2εO)+ψmεO(uM−Cm2εO), (25) so that the leader of group O values a weighted average of stayers’ and migrants’ utilities (O and M, respectively). The weights result from the relative size of the two subgroups and the parameter ψ∈(0,1), which accounts for a form of altruism towards the diaspora. We also assume that migration is costly, and model this cost—which is shared by stayers and migrants—as a quadratic function of the number of migrants, with C > 0.29 Second, the decision process becomes more complex, since the leader of group O chooses m at a preliminary stage, before determining her conflict strategy θO. She, however, takes into account (but does not interfere with) the strategy of the diaspora, which chooses a independently as in Section 3. This alternative version of the model implies that, by choosing m = m*, the leader of group O also selects a war- or peace-equilibrium, deciding whether or not to exploit the peace-wrecking or peace-building potential of international migration. As there are now four variables—θO, θE, a and m—which must be endogenously determined, the problem becomes less tractable and we cannot provide analytical solutions for their equilibrium values. In order to illustrate the possible outcomes of the two-stage model, we then resort to numerical simulations.30 4.2. Numerical examples We now present a few numerical examples, based on parameter values that, although largely arbitrary, may have a plausible interpretation. We start by considering the case of a potentially peace-building diaspora, that is, a situation in which higher values of m may lead to a transition from war to peace. Different from the benchmark model (as summarized by Figure 3), here the leader of group O chooses m so as to maximize the objective specified in Equation (25). By selecting the optimal size of the diaspora m*, she also determines whether conflict erupts or remains latent in the shadow of negotiation. Consider Figure 6, which is based on the following parameterization: εE = 200, εO = 100, y = 2, κ = 1, R = 20, γ = 0.5, δ = 0.1, χ = 0.06, η = 1, μ = 2.1 and ψ = 1. In both panels, higher levels of m are associated to peace (the green-shaded area). The final outcome of the model, however, is different. The left panel depicts a situation (C = 0.024, Z = 0.43) in which the leader of group O maximizes her objective by selecting a relatively high value of m, which makes her prefer to engage in a peaceful negotiation over the contested resource. Instead, the economy represented in the right panel (C = 0.03, Z = 0.44) ends up in war. This numerical exercise highlights two possible factors affecting the choice between war and peace: along with Z (a higher cost of peace makes the size of the peace area shrink), the cost of migration C also plays a role. If migration has a peace-building potential, but is too costly, it may not fulfill its pacifying potential. Indeed, a higher C may render negotiation less attractive: when the diaspora becomes large enough to bring about a peaceful settlement, the payoff of peace is not big enough to compensate for the high total cost of migration. Figure 6 View largeDownload slide Endogenous m: peace-building migration. Figure 6 View largeDownload slide Endogenous m: peace-building migration. Figure 7 illustrates the symmetric case of a potentially peace-wrecking diaspora. Here, a higher cost of migration may preserve peace by pushing the leader of group O to send less group members abroad, thus preventing the diaspora from reaching the threshold size beyond which it precipitates the origin country in a civil war. The common parameters for the two panels of Figure 7 are εE = 200, εO = 400, y = 2, κ = 1, R = 20, γ = 0.5, δ = 0.1, χ = 0.06, η = 1, μ = 2.1 and ψ = 1. The left panel is built using Z = 0.525 and C = 0.008, while for the right hand side panel we set Z = 0.49 and C = 0.01: we can see how a higher cost of migration keeps the diaspora within the peace region, whose size is determined by Z in the usual fashion. Figure 7 View largeDownload slide Endogenous m: peace-wrecking migration. Figure 7 View largeDownload slide Endogenous m: peace-wrecking migration. 5. Migration from both groups Another possible limitation of the benchmark model developed in Section 3 is that it allows migration from one group only, namely O, while all the members of group E are supposed to remain in the home country. To deal with this issue, we present an extension with diasporas from both groups, which can get actively involved in the homeland conflict. Introducing a second diaspora from group E significantly complicates the analysis, and prevents us from going as far as in the benchmark model, in terms of analytical results. We will thus derive thereafter a few results about the mechanisms at play, which can be compared with the single-diaspora model, and then resort to numerical simulations in order to gain further insight about the implications of the model. 5.1. Model setup and optimal choices We denote by mO and aO (mE and aE) the exogenous size of the diaspora related to group O (E) and its financial contribution, that is, the subsidy it gives to each soldier employed by its group of origin. We make the same assumptions as in the benchmark specification, regarding both the resident groups’ and the diasporas’ utility functions. For simplicity, we also make the same simplifying assumptions on the parameters, namely γ = 1/2, κ = 1, and η = 1. The two groups now have symmetric utility functions that, in case of war, write as   uE,w=(1−δ)((1−θE)y+aEθE+χs(AE,AO)R), (26) and   uO,w=(1−δ)((1−θO)y+aOθO+χ(1−s(AE,AO))R), (27) respectively. For given aE and aO, we can retrieve from first order conditions the two groups’ reaction functions, whose intersection corresponds to the following optimal shares of soldiers:   θE*(aE,aO)=χR(εO−mO)(εE−mE)(y−aO)((y−aO)(εE−mE)+(y−aE)(εO−mO))2, (28)  θO*(aE,aO)=χR(εO−mO)(εE−mE)(y−aE)((y−aO)(εE−mE)+(y−aE)(εO−mO))2. (29) The expressions of θE*(aE,aO) and θO*(aE,aO) allow us to determine AE*(aE,aO) and AO*(aE,aO), which are taken into account in the diasporas’ programs. In case of conflict, the leaders of the diasporas decide aE and aO so as to maximize   uME,w=(1+μ)y−aEθE*(aE,aO)(εE−mE)mE+(1−δ)χs(AE*(aE,aO),AO*(aE,aO))R, (30) and   uMO,w=(1+μ)y−aOθO*(aE,aO)(εO−mO)mO+(1−δ)χ(1−s(AE*(aE,aO),AO*(aE,aO)))R, (31) respectively. As in the benchmark model, the optimal contribution of each group of migrants is a piecewise function of the diaspora size. In particular, there exist m1,E, m2,E, m1,O and m2,O such that: if mE ≤ m1,E (respectively, mO ≤ m1,O), aE* (respectively, aO*) is equal to zero; if m1,E < mE < m2,E (respectively, m1,O < mO < m2,O), aE* (respectively, aO*) is strictly positive; if m2,E ≤ mE < εE (respectively, m2,O ≤ mO < εO), all the resident members of group E (respectively, O) are employed as soldiers (and paid out of the diaspora’s contribution).31 Although we cannot determine analytically how aE* and aO*, and subsequently θE* and θO*, vary with mE and mO, we can identify five possible regions depending on the values of mO and mE: AA when mE ≤ m1,E and mO ≤ m1,O, none of the two diasporas decides to finance the involvement of its group of origin in conflict ( aE*=aO*=0); AB when mE ≤ m1,E and m1,O < mO < m2,O, or when mO≤m1,O and m1,E<mE<m2,E, only one of the two diasporas chooses to contribute ( aE*>aO*=0, or aO*>aE*=0); BB when m1,E < mE < m2,E and m1,O < mO < m2,O, both diasporas get financially involved in the conflict in the homeland ( aE*>0, aO*>0); BC when m1,E < mE < m2,E and m2,O ≤ mO < εO, or when m1,O < mO < m2,O and m2,E ≤ mE < εE, both diasporas contribute ( aE*>0, aO*>0), and one of the two groups of residents allocates all its labor force to conflict ( θE*<θO*=1, or θO*<θE*=1); CC when m2,E ≤ mE < εE and m2,O ≤ mO < εO, both diasporas contribute ( aE*>0, aO*>0) and both groups of residents allocate all their labor force to conflict ( θE*=θO*=1). For ease of exposition and in order to allow for comparison with the benchmark model, we now restrict our attention to region BB only. 5.2. War versus peace In case of war, the utility functions of groups E and O depend on mE and mO through the optimal values aE*, aO*, θE* and θO*, which are all endogenously determined at equilibrium. In case of peace, utilities are given by Equations (19) and (20) from Section 3. Solving ui,p = ui,w (for i = E, O) yields the new threshold functions s˜E(mE,mO) and s˜O(mE,mO), which give the values of s that make each group indifferent between conflict and peaceful negotiation.32 In order to understand how the existence of a second diaspora affects the peace or war outcome in the origin country, we simulate the behavior of the model and look at what happens when we let mE vary in the alternative cases of a peace-building and a peace-wrecking potential of the diaspora related to group O. These two scenarios are described in Figures 8 and 9, which can be regarded as the two-diaspora counterparts of Figures 3 and 5 in Section 3. Figure 8 View largeDownload slide Low versus high mE, when mO has a peace-building potential. Figure 8 View largeDownload slide Low versus high mE, when mO has a peace-building potential. Figure 9 View largeDownload slide Low versus high mE, when mO has a peace-wrecking potential. Figure 9 View largeDownload slide Low versus high mE, when mO has a peace-wrecking potential. Panels (a) and (b) of Figure 8 depict s˜E(mO) and s˜O(mO) for two different values of mE. We set εE = 500, εO = 400, y = 2, κ = 1, R = 20, γ = 0.5, δ = 0.1, χ = 0.065, η = 1 and Z = 0.525. This vector of parameters ensures that the diaspora of group O has a peace-building potential. In Figure 8(a), mE is set to 60, while we increase it to 120 in Figure 8(b). The simulations reveal that a larger mE increases the threshold value mO^ that triggers a switch from war to peace. Said differently, the existence of a larger diaspora emanating from group E makes it harder for the diaspora of group O to fulfill its peace-building potential. This is in line with the mechanism emphasized in the single-diaspora setting, namely that a diaspora makes its group of origin more willing to go to war, as its relative strike force is boosted by migrants’ contribution. Figure 9 generates the case of a potentially peace-wrecking diaspora by modifying the values of εE (namely, from 500 to 200) and χ (from 0.065 to 0.08). Again, we set mE equal to 60 in Figure 9(a), and 120 in Figure 9(b). A larger mE is associated with a higher threshold value m¯O, so that it becomes more difficult for the diaspora of group O to fulfill its peace-wrecking potential. Otherwise said, when the diaspora of group E is larger, it takes a larger migration from group O for its financial contribution to ignite conflict in the origin country. 5.3. Discussion To sum it up, extending the model to two diasporas allows us to draw a few reassuring conclusions regarding the robustness of our analysis. As far as the rival diaspora is not too large (region AA, where no diaspora subsidizes conflict, or AB, where only the diaspora from group O intervenes), the single-diaspora model leads to the same qualitative results as the two-diaspora extension.33 When the rival diaspora is larger and gets actively involved in the conflict (region BB), each diaspora attenuates the effect of the other, be it peace-building or peace-wrecking. Indeed, a diaspora makes its own group more willing to go to war and its rival group more willing to negotiate, and a rival diaspora has the opposite effects. Finally, consistent with Section 3, we do not delve into the analysis of very large diasporas (regions BC and CC), which would have the unrealistic effect of pushing the group of origin to employ all its members as soldiers. 6. Conclusion We propose a model of conflict to explore how a diaspora, by financially supporting its group of origin, may affect the intensity and likelihood of war in the homeland. We find that, if large enough, a diaspora is willing to contribute to the war effort of its group of origin. In case of actual conflict, this fuels the intensity of war, pushing the origin group to allocate a higher share of its members to fighting. However, the impact of the diaspora is not always peace-wrecking, as the strengthened bargaining power that it confers to its group of origin may deter the rival group from fighting and make the peace process more likely. In particular, we show that factors regulating the costs of war and peace in the home country determine whether the diaspora is more likely to act as a peace-building or peace-wrecking force. Although based on a few simplifying assumptions—namely, that migration is exogenous and concerns only one of the two resident groups—our benchmark model is rich enough to account for several aspects and determinants of the interaction between real-world diasporas and conflict in sending countries. When we extend the basic model so as to relax the above assumptions, we find that most of our main results carry through, thus showing that our theoretical framework is fairly general. In addition, we are able to obtain a few complementary findings related to the strategic management of migration by political leaders. As directions for further research, we would suggest considering complementary channels, both direct and indirect, through which the diaspora might affect conflict dynamics. In particular, the lobbying activity of diasporas might play an important direct role, in addition to the size effect and targeted remittances investigated here. As far as indirect channels are concerned, emigration may also shape the incentives to engage in conflict in the home country through non-targeted financial flows (i.e. private remittances), as well as productivity and price effects. For instance, in a setting with decreasing marginal productivity of labor, the diaspora may be more likely to have a peace-building role: by eroding the size of the origin group, emigration may in fact cause its productivity to increase, thereby raising the opportunity cost of conflict. Exploring these (and other related issues) would allow us to better gauge the importance of diasporas for the evolution and outcome of inter-group competition in the sending economy. Acknowledgements The authors are thankful to Fiona Adamson, José de Sousa, Frédéric Docquier, David Levine, Anna Lindley, Christopher McDowell, Alice Mesnard, Gerard Padro i Miquel, Hillel Rapoport, Dominic Rohner and Olivier Sterck for their comments on earlier drafts. The authors also thank the Editor and two anonymous referees for very helpful comments. The authors would like to express their gratitude to seminar participants at ULB (Brussels), IRES - UCLouvain (Louvain-la-Neuve), THEMA (Cergy-Pontoise), Dauphine (Paris), City University (London) and Sciences Po (Paris), as well as participants to the PET 2014 in Seattle, SMYE 2015 in Gent, CSAE 2015 conference on ‘Economic Development in Africa’ in Oxford, 2nd DIAL Development Conference in Paris, 2015 ASSET conference in Granada, IMI conference on ‘The Changing Face of Global Mobility’ in Oxford, 2016 International Conference on Migration and Development in Florence, 2016 EEA–ESEM Congress in Geneva, 28th SIEP Conference in Lecce and 7th Meeting of the Society for the Study of Economic Inequality (ECINEQ) in New York City, for useful and lively discussions. Funding Marion Mercier acknowledges financial support from the Marie Curie-Skłodowska Research Fellowship Program of the European Commission (H2020 Horizon), project MIGWAR, number 657861. This research is part of the ARC project 15/19-063 on ‘family transformations’ (French speaking community of Belgium). Footnotes 1 Horst (2008), among others, also reports such a variety of transnational political engagements, putting special emphasis on financial contributions. 2 Diasporas may also play a role for conflict in the host country, as it happened for the Palestinian diaspora in the context of the Lebanon war for instance. Discussing such cases remains, however, outside the scope of this article. 3 In reality, migrants also send funds to their origin country as remittances to their families. Private remittances are not neutral with respect to conflict, since they modify the recipients’ budget constraint and then their opportunity cost to get involved in civil war or become activists. Moreover, the existence of a conflict at home affects migrants’ propensity to remit (see in particular Carling et al. (2012) and Vargas-Silva (2016)). However, the analysis of the specific impact of private remittances on conflict is beyond the scope of this article. 4 Gunaratna (2003) estimates that the LTTE had an annual income close to 100 million dollars, of which the diaspora had contributed at least 60 million per year. 5 See, for instance, Arthur (1991); Adamson (2002); Horgan and Taylor (1999); Cox (1997). 6 The highly influential Irish Northern Aid Committee, also known as Noraid, was openly supportive of IRA’s armed struggle but progressively softened its stance. The 1990s saw the emergence of a new lobby group, the Americans for a New Irish Agenda (ANIA), which played a paramount role in lobbying the Clinton administration to promote a peace-building process in Northern Ireland. 7 Only older generations maintained a strong pro-war attitude. 8 The expertise and knowledge of diaspora members have been used to mediate in national reconciliation conferences and workshops around the country. In addition to their lobbying activities, diaspora members have also both formally and informally collected money to meet humanitarian and development needs. Diaspora Somalis have also been active in fueling and shaping the political debate at home (Menkhaus, 2006). 9 According to Hockenos (2003), more than 50 million dollars flowed from the diaspora toward the HDZ between 1991 and 1995, during the hot conflict stage. 10 More than 20 Kenyan diaspora-federated organizations, representing over 250,000 members, cooperate through the Kenya Diaspora Alliance (KDA), aiming at resolving conflicts at home and lobbying for a peace-building process. 11 The Eritrean diaspora intervened in the independence war mostly by providing funds for the armed struggle of the secessionist groups (Hockenos, 2003). 12 Group O can also be regarded as the ‘oppressed’ one, but this interpretation is not necessary. 13 Assuming that migrants are interested in the public good contested in the homeland is consistent with examples of diasporas being highly involved in the political situation in their home country, which may also be decisive for their opportunity to migrate back home. Although we do not explicitly model them, the determinants of η might be as diverse as the geographical distance between the origin and destination countries, the strength of migrants’ link with their group of origin (which may depend on whether they have family members back home), their willingness to return in the origin country, or the time they spent in migration. Intuitively, cultural assimilation and integration in the host country may also weaken the link with the source country. 14 Contest functions of this type, whose theoretical foundations are outlined in Jia et al. (2013) and Garfinkel and Skaperdas (2007), are widely used in the literature on conflict. 15 We do not assume γ larger or smaller than 1/2 so there is no prior on which group should have a relative advantage in the conflict. 16 Intervening or not in the conflict in the homeland can be a source of dispute among diaspora members, in the first place. We sidestep this issue, in order to focus on the interaction between the diaspora and the resident groups. 17 Considering that migrants cannot decide to migrate back in order to become soldiers is a simplifying assumption, which allows us to focus on the specificity of abroad-living actors involved into a distant conflict. Relaxing this assumption would significantly complicate the analysis, as the diaspora would have two variables to decide upon—namely its financial contribution and its human capital contribution. However, intuitively, this should yield qualitatively comparable results, since, in our setting, migrants’ financial contribution can only affect the intensity of war through the human resources which are dedicated to conflict. As far as residents and migrants have the same productivity in fighting, whether a soldier is a resident or a return migrant should not matter. 18 If we were to consider negative values for a, they could be interpreted as the diaspora withdrawing capital from the home country. 19 The equilibrium contribution is also a growing function of η, the parameter which captures diaspora members’ interest in the access of their group of origin to the contested resource. 20 The complete expression for m2, which is rather complicated, is given in Appendix A. 21 In this setting, an additional increase of the size of the diaspora has a U-shaped effect on the diaspora’s involvement. First, when the diaspora becomes bigger, the contribution is dissolved between more migrants which allows the subsidy a*(m) to diminish. At the same time, the shrink of the number of residents makes it more and more difficult to prevail in the conflict, and thus at one point the compensation from the diaspora which ensures that all the resident members remain soldiers needs to be bigger. 22 Recall that εE < (1 – δ)m also ensures that θE* increases with a* (see point (ii) of Proposition 2). 23 Note that the Nash-bargaining process we use is symmetric, as the two groups’ surpluses have the same weight in the objective. Asymmetry, however, may arise indirectly through the parameter γ, which affects the war outcomes of groups E and O. Here, the results are displayed under Assumption 1, and no such asymmetry is possible. 24 If the international community takes a stronger stance against the involvement of transnational networks in armed conflicts, this can take the form of increased police controls, which would increase the cost of conflict in sending countries, or high-level political activity intended to favor conflict resolution, which would actually decrease the cost of peace. 25 As stressed in Section 2, financial participation was also nearly mandatory for other groups of migrants, in particular the Croatian diaspora before independence, and Eritrean migrants who, after independence, were asked by the government to contribute 2% of their monthly income to the newly formed state (Fessehatzion, 2005); such contributions were not strictly compulsory, but largely perceived as a duty (Koser, 2007). 26 Notice also that the likelihood of the peace-wrecking scenario is in turn positively linked to increases in Z and χ, which can both be related to a surge in nationalism. 27 One may also speculate that Castro let the size of group O shrink substantially through migration, so as to minimize the risk of open conflict. 28 One could also think about migration as a fully decentralized decision taken by individual agents who compare, at any moment in time, utility at home and abroad. This (dynamic) extension of the basic model, which implies that both m and a are outside the influence of the leader of group O, is analyzed in the working paper version of this article (Mariani et al., 2017). 29 There can be multiple justifications for assuming an increasing marginal cost of emigration. We can think, for instance, to some form of congestion externality related to migration, decreasing returns to migrants’ labor, or that receiving countries take a stronger anti-immigration stance as m increases. 30 Some intermediate analytical results, such as the groups’ reaction functions and the characterization of different regimes, are available upon request. 31 The threshold values m1,E, m2,E, m1,O and m2,O are obtained following the same logic as Section 3.2.1, when determining Equation 12. In this extension, however, we must take into account that both migration and remittances are also allowed for group E, and influence the conflict equilibrium of the model. 32 We can further assume that the sharing rule negotiated by the two groups in case of peace is the outcome of a Nash-bargaining process, just as in the benchmark model. 33 The only difference being that, in region AB, the ‘passive’ diaspora triggers a size effect that, by weakening its group of origin, reinforces the role of the active one. References Adamson F. ( 2002) Mobilizing for the transformation of home: politicized identities and transnational practices. In Al-Ali N., Koser K. (eds) New Approaches to Migration? Transnational Communities and the Transformation of Home , pp. 155– 168. London: Routledge. Arthur P. ( 1991) Diasporan intervention in international affairs: Irish America as a case study. Diaspora: A Journal of Transnational Studies , 1: 143– 162. Google Scholar CrossRef Search ADS   Barsbai T., Rapoport H., Steinmayr A., Trebesch C. ( 2017) The effect of labor migration on the diffusion of democracy: evidence from a former Soviet Republic. American Economic Journal: Applied Economics , 9: 36– 69. Google Scholar CrossRef Search ADS   Batista C., Vicente P. C. ( 2011) Do migrants improve governance at home? Evidence from a voting experiment. The World Bank Economic Review , 25: 77– 104. Google Scholar CrossRef Search ADS   Beyene H. G. ( 2015) Are African diasporas development partners, peace-makers or spoilers? The case of Ethiopia, Kenya and Nigeria. Diaspora Studies , 8: 145– 161. Google Scholar CrossRef Search ADS   Blattman C., Miguel E. ( 2010) Civil war. Journal of Economic Literature , 48: 3– 57. Google Scholar CrossRef Search ADS   Brinkerhoff J. M. ( 2011) Diasporas and conflict societies: conflict entrepreneurs, competing interests, or contributors to stability and development? Conflict, Security and Development , 11: 115– 143. Google Scholar CrossRef Search ADS   Carling J., Erdal M. B., Horst C. ( 2012) How does conflict in migrants’ country of origin affect remittance-sending? Financial priorities and transnational obligations among Somalis and Pakistanis in Norway. International Migration Review , 46: 283– 309. Google Scholar CrossRef Search ADS   Chauvet L., Mercier M. ( 2014) Do return migrants transfer political norms to their origin country? Evidence from Mali. Journal of Comparative Economics , 42: 630– 651. Google Scholar CrossRef Search ADS   Cochrane F. ( 2007) Irish-America, the end of the IRA’s armed struggle and the utility of soft power. Journal of Peace Research , 44: 215– 231. Google Scholar CrossRef Search ADS   Collier P., Hoeffler A. ( 2004) Greed and grievance in civil war. Oxford Economic Papers , 56: 563– 595. Google Scholar CrossRef Search ADS   Constant A. F., Zimmermann K. F. ( 2016) Diaspora economics: new perspectives. International Journal of Manpower , 37: 1110– 1135. Google Scholar CrossRef Search ADS   Cox M. ( 1997) Bringing in the ‘international’: the IRA ceasefire and the end of the Cold War. International Affairs , 73: 671– 693. Google Scholar CrossRef Search ADS   Docquier F., Lodigiani E., Rapoport H., Schiff M. ( 2016) Emigration and democracy. Journal of Development Economics , 101: 1– 21. Docquier F., Rapoport H. ( 2003) Ethnic discrimination and the migration of skilled labor. Journal of Development Economics , 70: 159– 172. Google Scholar CrossRef Search ADS   Docquier F., Ruyssen I., Schiff M. ( 2017) International migration: pacifier or trigger for military conflicts? Journal of Development Studies , forthcoming. Esteban J., Ray D. ( 2008) On the salience of ethnic conflict. The American Economic Review , 98: 2185– 2202. Google Scholar CrossRef Search ADS   Esteban J., Ray D. ( 2011) A model of ethnic conflict. Journal of the European Economic Association , 9: 496– 521. Google Scholar CrossRef Search ADS   Fair C. C. ( 2007) The Sri Lankan Tamil diaspora: sustaining conflict and pushing for peace. In Smith H., Stares P. B. (eds) Diasporas in Conflict: Peace-Makers or Peace-Wreckers ? pp. 172– 195. Tokyo: United Nations Publications. Fessehatzion T. ( 2005) Eritrea’s remittance-based economy: conjectures and musings. Eritrean Studies Review  4: 165– 184. Garfinkel M. R., Skaperdas S. ( 2007) Economics of conflict: an overview. Handbook of Defense Economics , 2: 649– 709. Google Scholar CrossRef Search ADS   Grugel J., Kippin H. ( 2007) The Cuban diaspora. In Smith H., Stares P. B. (eds) Diasporas in Conflict: Peace-Makers or Peace-Wreckers ? pp. 153– 171. Tokyo: United Nations Publications. Gunaratna R. ( 2003) Sri Lanka: feeding the Tamil Tigers. In Ballentine K. (ed.) The Political Economy of Armed Conflict: Beyond Greed and Grievance, pp.  197– 223. Lynne Rienner Boulder, CO: Lynne Rienner. Hockenos P. ( 2003) Homeland Calling: Exile Patriotism and the Balkan Wars . Ithaca, NY: Cornell University Press. Horgan J., Taylor M. ( 1999) Playing the ‘Green Card’ – financing the provisional IRA: part 1. Terrorism and Political Violence , 11: 1– 38. Google Scholar CrossRef Search ADS   Horowitz D. L. ( 1985) Ethnic Groups in Conflict . Berkeley, CA: University of California Press. Horowitz D. L. ( 1998) Structure and strategy in ethnic conflict. In Pleskovic B., Stiglitz J. E. (eds) Annual World Bank Conference on Development Economics , pp. 345– 370. Washington, DC: World Bank. Horst C. ( 2008) The transnational political engagements of refugees: remittance sending practices amongst Somalis in Norway: analysis. Conflict, Security & Development , 8: 317– 339. Google Scholar CrossRef Search ADS   Jia H., Skaperdas S., Vaidya S. ( 2013) Contest functions: theoretical foundations and issues in estimation. International Journal of Industrial Organization  31: 211– 222. Google Scholar CrossRef Search ADS   Joshi M. ( 1996) On the razor’s edge: the liberation tigers of Tamil Eelam. Studies in Conflict and Terrorism , 19: 19– 42. Google Scholar CrossRef Search ADS   Koinova M. ( 2011) Diasporas and secessionist conflicts: the mobilization of the Armenian, Albanian and Chechen diasporas. Ethnic and Racial Studies , 34: 333– 356. Google Scholar CrossRef Search ADS   Koser K. ( 2007) African diasporas and post-conflict reconstruction: an Eritrean case study. In Smith H., Stares P. B. (eds) Diasporas in Conflict: Peace-Makers or Peace-Wreckers ? pp. 239– 252. Tokyo: United Nations Publications. Mariani F. ( 2007) Migration as an antidote to rent-seeking? Journal of Development Economics , 84: 609– 630. Google Scholar CrossRef Search ADS   Mariani F., Mercier M., Verdier Th. ( 2017) Diasporas and conflict. CEPR Discussion Paper 11926. Menkhaus K. ( 2006) The rise of Somalia as a Diaspora Nation: impact on peace-building, governance and development. Paper presented at the University for Peace Expert Forum on Capacity Building for Peace and Development: Roles of Diaspora. Toronto, Canada, October 19–20. Mohamoud A. A. ( 2006) African diaspora and post-conflict reconstruction in Africa. Copenhagen: Danish Institute for International Studies (DIIS). Orjuela C. ( 2008) Distant warriors, distant peace workers? Multiple diaspora roles in Sri Lanka’s violent conflict. Global Networks , 8: 436– 452. Google Scholar CrossRef Search ADS   Pfutze T. ( 2012) Does migration promote democratization? Evidence from the Mexican transition. Journal of Comparative Economics , 40: 159– 175. Google Scholar CrossRef Search ADS   Pirkkalainen P., Abdile M. ( 2009) The Diaspora-Conflict-Peace-Nexus: A Literature Review . Jyväskylä: University of Jyväskylä, Diaspeace Project. Preotu V. ( 2016) Emigration as a pacifying force? Geneva School of Economics and Management Working Paper 16033. Roth A. ( 2015) The role of diasporas in conflict. Journal of International Affairs , 68: 289. Shain Y. ( 2002) The role of diasporas in conflict perpetuation or resolution. SAIS Review of International Affairs , 22: 115– 144. Sheikh H., Healy S. ( 2009) Somalia’s Missing Million: The Somali Diaspora and Its Role in Development . New York: United Nations Development Programme. Skrbiš Z. ( 2000) Long-Distance Nationalism . Aldershot: Ashgate. Smith H., Stares P. B. ( 2007) Diasporas in Conflict: Peace-Makers or Peace-Wreckers?  Tokyo: United Nations Publications. Spilimbergo A. ( 2009) Democracy and foreign education. The American Economic Review , 99: 528– 543. Google Scholar CrossRef Search ADS   Van Hear N., Cohen R. ( 2017) Diasporas and conflict: distance, contiguity and spheres of engagement. Oxford Development Studies , 45: 171– 184. Google Scholar CrossRef Search ADS   Vargas-Silva C. ( 2016) Remittances sent to and from the forcibly displaced. Journal of Development Studies , 53: 1835– 1848. Google Scholar CrossRef Search ADS   Appendices A. Complementary results Here we report the analytical expressions for m2, m^ and m¯, referred to in Section 3, but omitted for ease of exposition. A.1. Expression for m2 in Section 3.2.2 The complete expression for m2, obtained solving θO*(a,m)=1, is   m2=−(4yεE)2−(δ2εEχR)2+8yεEδχR(2δεE−3(1−δ)εO)−Ω1/3(δ2εEχR+Ω2−4y(2εE+3εO))12yΩ1/3, (A.1) with   Ω=(4yεE)3+24y2εEχR(5(δεE)2−3εO(1−δ)(4δεE−3(1−δ)εO))−12y(εEχR)2δ3(2δεE−3(1−δ)εO)+(δ2εEχR)3+243yεE(εO−δ(εE+εO))yχR((4yεE)2−(δεE+9(1−δ)εO)2+54((1−δ)εO)2+(1−δ)δ3εEεO(χR)2). A.2. Expression for m^ and m¯ in Proposition 4 Solving ui,p = ui,w (for i = E, O) yields   m^=4(Z−δy)(εO+εE)−((3−δ)δεE+(1+δ)εO)χR−(εO−δ(εE+εO))(1−δ)ϕχR(1−δ)3χR−ϕ, (A.2) and   m¯=4(Z−δy)(εO+εE)−((3−δ)δεE+(1+δ)εO)χR+(εO−δ(εE+εO))(1−δ)ϕχR(1−δ)3χR−ϕ, (A.3) with ϕ=(1+δ)χR−4(Z−δy). B. Endogenous m: the ‘global social planner’ case Different from the benchmark model, here we consider a passive diaspora, whose size and involvement in conflict are both determined by the leader of its group of origin. In this sense, the leader of group O becomes a transnational social planner who centralizes all the decisions that are relevant for her group’s members, be they migrants or stayers. B.1. Setup We consider an economy with only two groups, O and E, where only members of group O can migrate. While the leader of group E behaves as in Section 3, that of group O must now decide simultaneously θO and m, thereby determining the size of the diaspora, which becomes an endogenous variable. In the same fashion as in Section 4, we introduce a quadratic cost of migration, so that the total cost of sending m members of group O abroad is given by Cm2. Different from Section 4, where the diaspora could autonomously decide its degree of participation to conflict in the origin country, we further assume that the leader of group O can redistribute resources across all group members in such a way that everybody enjoys the same level of utility. Therefore, in case of war, her objective becomes   uO,w=(εO−m)(1−θO)y(1−δ)+m(1+μ)y−Cm2εO+χ(1−s(AE,AO))(1−δ)R, (A.4) which can be compared with Equation (6) in the main text. In case of peace, we will instead have   uO,p=(εO−m)y+m(1+μ)y−Cm2εO+χ(1−s)R−Z, (A.5) which is the counterpart of Equation (20) in the benchmark model. As mentioned before, the objective functions of group E, uE,w and uE,p, are the same as in Section 3. B.2. Solving the model We can now solve the model along the lines of Section 4, that is, taking m as given. We then let the leader of group O select the value of m which maximizes her objective; by choosing m, she will implicitly choose between war and peace, very much in the spirit of Section 4.1. We start by finding the intersection of the two groups’ reaction functions, thus determining the equilibrium values of the θ’s in case of conflict, that is,   θE*(m)=χRγ(1−γ)εOεEy((1−γ)κεO+γεE)2, (A.6) and   θO*(m)=χRγ(1−γ)κεO2εEy(εO−m)((1−γ)κεO+γεE)2. (A.7) A first interesting result emerges: while θE* does not depend on m, θO* is increasing in m, which means that migration has an inherently peace-wrecking potential. From θE*(m) and θO*(m) we can obtain AE*(m) and AO*(m), that is, the equilibrium sizes of the two armies depending on m, as well as the utilities of the two groups in case of war. By comparing the war and peace outcomes of the two groups (i.e. solving ui,p = ui,w, for i = E, O), we are able to identify the threshold functions s˜E(m) and s˜O(m), which give the values of s such that, for each possible m, the two groups are indifferent between open conflict and peaceful settlement. In particular, after setting γ = 1/2, κ = 1 and η = 1 as in Section 3, we obtain   s˜E(m)=Z−δyχR+(1−δ)εE2(εE+εO)2, (A.8) and   s˜O(m)=−(εOZ−(εO−m)δy)εOχR+εE2+2εEεO+δεO2(εE+εO)2. (A.9) It can be seen that s˜E does not depend on m, while s˜O decreases in m. We can then claim the following. Proposition A.1 In the global social planner case, migration can only be peace-wrecking. In fact, if there is an intersection between the two threshold functions, s˜O(m) crosses s˜E(m) from above, meaning that there exists a value m¯′ of m, such that for any m>m¯′, war is the only possible outcome. Such peace-impeding level of migration is equal to   m¯′=εO(2(εE+εO)2(δy−Z)+(2εEεO+δ(εE2+εO2))χR)(εE+εO)2δy. (A.10) As far as the choice of m is concerned, the leader of group O will compare the possible utility she can reach under the two alternative scenarios of peace (i.e. for m≤m¯′) and war ( m>m¯′), and select m = m* so as to attain a global maximum of utility. Restricting our attention to interior solutions only (i.e. 0 < m* < εO), it can be shown that   m*={(δ+μ)y2Cif C<C^(δ+2μ)y4Cif C≥C^, (A.11) where   C^=(εE+εO)2(3δ+4μ)δy28εO(2(εE+εO)2(δy−Z)+(2εEεO+δ(εE2+εO2))χR). (A.12) This results lends itself to the following interpretation: if migration is not very costly, the leader of group O will try to exploit the peace-wrecking potential of migration and choose the size of the diaspora accordingly. If instead the cost of migration is high, the two groups will negotiate a peaceful sharing of the contested resource, a situation associated with a weaker migration outflow. © The Author(s) (2018). Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Economic Geography Oxford University Press

Diasporas and conflict

Loading next page...
 
/lp/ou_press/diasporas-and-conflict-h67bgkHoY6
Publisher
Oxford University Press
Copyright
© The Author(s) (2018). Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com
ISSN
1468-2702
eISSN
1468-2710
D.O.I.
10.1093/jeg/lby014
Publisher site
See Article on Publisher Site

Abstract

Abstract We build a model of conflict in which two groups contest a resource and must decide on the optimal allocation of labor between fighting and productive activities. In this setting, a diaspora emanating from one of the two groups can get actively involved in conflict by transferring financial resources to its origin country. We find that the diaspora influences the war outcome and, above a certain size, contributes to the escalation of violence. Given the characteristics of the conflict equilibrium, the two groups of residents prefer to negotiate a peaceful settlement if there exists a sharing rule that makes both of them better off than war. We then identify the characteristics of the economy such that the diaspora acts as a peace-wrecking force or triggers a transition towards peace. Finally, we develop two extensions of the model, respectively, accounting for endogenous migration and the possibility of migration from both groups. Overall, our theory can help us make sense of several features of the interaction between real-world diasporas and conflict. 1. Introduction Poor countries are often plagued by civil wars and, in many cases, source of sizable migration flows. There is also abundant evidence that diasporas can play a major role in the evolution of conflict in the origin country, through various channels that range from political lobbying to financial support and direct involvement in fighting. In this article, we build a theoretical framework to understand how diasporas can affect conflict in the origin country, and act as a peace-building or peace-wrecking force. By doing this, we hope to fill a gap in the economic literature, which has so far overlooked the interaction between migrant groups and conflict in the homeland. The role of diasporas in conflict has instead attracted a lot of attention from political scientists. Horowitz (1985, 1998) emphasizes how, in the context of ethnic conflict, group members value group success per se, regardless of the individual benefits derived from victory. This consideration can easily be extended to migrants who maintain strong interests in conflict at home, and lies at the basis of a rich qualitative literature directly tackling the involvement of diasporas in homeland violence. Brinkerhoff (2011) provides a very interesting discussion of this literature and reviews the diverse modes of intervention that different diasporas have adopted. She emphasizes, in particular, the role of economic remittances (or financial contributions directly targeted towards armed groups and political parties), philanthropy, human capital support and political influence from abroad.1 Through all these means, diasporas can be at once conflict entrepreneurs, agents of competing interests and contributors to peace. This considerable heterogeneity in the role of diasporas in conflicts and post-conflict situations can be related, according to Van Hear and Cohen (2017), to multiple diaspora characteristics, such as location, resources and social capital. Overall, recent research in political science highlights the increasing importance of abroad-living communities as decisive transnational actors, which use various tools in order to influence the politics of the home country, eventually fostering violence or promoting conflict resolution (Roth, 2015).2 On the contrary, as mentioned above, the economic literature has remained so far quite silent on the role of diasporas in shaping conflict in the origin country. First, the vast literature considering the possible impact of emigration on sending countries’ outcomes has overlooked the onset and intensity of civil conflict as relevant variables of interest. Even the few papers interested in the consequences of migration for inter-group competition in the sending country (Docquier and Rapoport, 2003; Mariani, 2007) have not modeled conflict and the choice between war and peace. Some recent (and mostly empirical) studies, however, have shown that migrants can somehow shape institutions and politics in the sending country. For instance, Spilimbergo (2009) provides evidence that foreign students have a positive impact on democracy in the home country, while Docquier et al. (2016) emphasize a positive effect of emigration on institutional development in the sending country. Consistent with these cross-country results, a few micro-oriented papers document the impact of migration on political participation and opinions in the origin communities. In particular, Batista and Vicente (2011) find that Cape Verdean nonmigrants living in more migration-intensive localities exhibit higher demand for political accountability, Chauvet and Mercier (2014) show that Malian return migrants transfer electoral norms to their origin communities, notably in terms of participation, while Pfutze (2012) puts forward that migration increases the probability that an opposition party wins a municipal ballot in Mexico. Finally, in the case of Moldova, Barsbai et al. (2017) highlight the role of (return) migration in the transfer of preferences for democracy to the home country. Second, the otherwise rich literature on conflict tends to neglect the role played by diasporas. As far as empirical studies are concerned, the only exception has long been Collier and Hoeffler (2004), who highlight a positive correlation between the proportion of migrants in the USA and the probability of conflict in the home country, thus suggesting that diasporas may be a risk factor in the re-ignition of wars. More recently, Docquier et al. (2017) find that bilateral migration increases the likelihood of interstate conflict. As far as domestic conflicts are concerned, Preotu (2016) reports that emigration to developed countries can decrease the incidence of civil war in the countries of origin. What is still missing, however, is a proper theoretical framework to understand through which channels migrants influence the evolution of conflict in the origin country. As pointed out by Blattman and Miguel (2010), ‘an important limitation of the existing theoretical work on armed conflict causes [is] its almost exclusive focus on the internal armed groups’ decision of whether or not to fight’. This article is a first step in this direction, and thus contributes to the research agenda outlined by Constant and Zimmermann (2016). We present a model of conflict in which two groups contest a resource that can be consumed as a group-specific public good. Open conflict requires labor and involves some destruction of resources. Within each group, agents, who are ex ante identical, collectively decide on the optimal allocation of labor between direct participation to the conflict (as soldiers or activists) and productive activities. In this setting, we introduce a diaspora emanating from one of the two groups. In case of conflict, migrants can decide to provide funding to their group of origin (i.e. subsidize its war effort), thus affecting the intensity and outcome of conflict.3 Given the characteristics of the implied conflict equilibrium, the two groups of residents may choose to negotiate a peaceful settlement if there exists a sharing rule that makes both of them better off than war. Our analysis highlights the role that migration can play in the escalation of violence and resolution of conflict. Our contribution is threefold. First, we show that there exists a threshold diaspora size above which migrants provide a positive contribution to the war effort of their group of origin. This contribution increases with the size of the diaspora, leading in turn to an increase in the share of fighters in the origin group. Second, we also find that the peace—war tradeoff is affected by the diaspora, which can play either a peace-building or a peace-wrecking role. In particular, we show that it is more likely to act as a peace-building force in cases when negotiation is more costly, productivity is lower (which reduces the opportunity cost of violence) and/or the amount of contested resources is lower. Furthermore, we also show how the critical size that the diaspora needs to attain in order to trigger a switch from war to peace (and vice versa) depends on the size of the two resident groups. Such critical size notably turns out to be larger when the rival group is more numerous. Finally, the last part of the article extends our basic framework to two extensions: endogenous migration and multiple diasporas. In the first case, this allows us to highlight how migration costs interact with the group incentives for conflict to determine a peace-building or peace-wrecking equilibrium. The second extension uncovers the fact that diasporas act as strategic substitutes in terms of conflict activation or resolution: each diaspora attenuates the effect of the other, be it in a peace-building or peace-wrecking regime. The rest of the article is organized as follows. Section 2 describes a few case studies, which have received important attention from the political science literature and motivate our approach. The benchmark model is set up and solved in Section 3, and the results are interpreted in light of the previously cited case studies. Section 4 considers an extension of the benchmark model with endogenous migration, resulting from the strategic choice of the group of origin, while the possibility of multiple diasporas (i.e. migration from both groups), is dealt with in Section 5. Finally, Section 6 concludes and proposes some directions for future research. 2. Case studies The involvement of diasporas in homeland conflicts has been documented by qualitative research in different fields. Here we provide a (non-exhaustive) review of some well-known cases, in order to further motivate our analysis and highlight some characteristics of the peace-building or peace-wrecking role of migrant communities that our theory tries to make sense of. We will refer to these case studies when interpreting the main results of our model. 2.1. Sri Lanka One of the best known cases of conflict deeply shaped by the diaspora’s intervention is the Sri Lankan Civil War, which opposed the Tamil and the Sinhalese between 1983 and 2009. Starting from the early 1980s, Tamil migrants provided strong financial support to the main Tamil armed group in Sri Lanka, the Liberation Tigers of Tamil Eelam (LTTE). The diaspora, which relied on a well-organized global network to channel funds to the fighters on a very large scale, has been described by Joshi (1996) as the ‘economic backbone of the militant campaign’, and contributed significantly to sustaining the conflict.4 In addition to favoring the escalation of violence through massive financial support to its group of origin, the Tamil diaspora undertook a relentless lobbying activity aimed at mobilizing international opinion (Gunaratna, 2003; Fair, 2007; Orjuela, 2008). Eventually, however, at the end of the 1990 s, most of the main migrants’ host countries labeled the LTTE as a Foreign Terrorist Organization. In the aftermath of the 9/11 attacks, the suspicion over the funds sent by the Tamil migrant community became even stronger, leading to a change in the role of the diaspora, which started to support nonviolent conflict resolution and power-sharing settlements (Fair, 2007; Orjuela, 2008). 2.2. Ireland The Irish community in the USA is usually regarded as a decisive player for the evolution of conflict in Northern Ireland, and has been the object of a substantial amount of research in political science.5Cochrane (2007), among others, argues that Irish-American played a vital role in the decision of the Provisional IRA to terminate its paramilitary campaign in 2005. Over time, the Irish diaspora shifted from open support to armed struggle (with financial donations that helped IRA intensify its armed campaign) to a peace-building attitude based on soft power, as the objective of powerful civil society organizations gradually changed from a ‘united Ireland’ to a more process-oriented request of a well-balanced peace process.6 According to Cochrane (2007), this evolution in political views corresponded to (i) the transformation of Irish-American ‘from refugee/immigrant community to integrated, moneyed and highly networked sector of the indigenous population’, (ii) the demographic decline of the Irish diaspora, induced by smaller migration rates and (iii) the reduced tolerance of violence by the Irish-American and the higher cost of funding political groups abroad, in the aftermath of 9/11. While becoming more integrated in the American social fabric, the Irish diaspora also became less heavily concerned with the situation in Northern Ireland.7 2.3. Somalia Somali emigration probably displays more heterogeneity than other diasporas. First of all, as pointed out by Sheikh and Healy (2009), a first wave of essentially economic migration has been followed, in the 1990s, by conflict-driven migration. Second, the Somali diaspora is made up of different sub-diasporas, each one with a different reference group (or clan) in the home country. Third, the diaspora has contributed to both peace-wrecking and peace-building efforts, in different times and regions. Until the early 1990s, Somalis in the diaspora were strongly pressured by local clan representatives to support the fighting effort of their group of origin, thus acting as fundraisers for clans militias. The decision of Somali migrants to finance conflict, as noticed by Mohamoud (2006), may also have resulted from (i) opportunistic motivation, with diaspora members donating funds to faction leaders and militia in the hope of obtaining power and government positions at the issue of conflict and (ii) disillusionment and frustration about the failure of ongoing peace negotiations. Along with this essentially peace-wrecking (or conflict-perpetuation) role, members of the Somali diaspora—especially more recent migrants, and in specific regions such as Somaliland—have also acted as promoters of peace, good governance and development and have undertaken peace-building initiatives, which have played an important and effective role.8 As far as the diaspora’s means of intervention are concerned, remittances at the clan level have been used not only to sustain war, but also to finance compensational payments (diya) deemed necessary for the reconciliation process between clans. Horst (2008) also highlights how diaspora remittances used to buy arms may have produced peace-building effects, by deterring violence from other groups. 2.4. Croatia Skrbiš (2000) emphasizes that financial participation was nearly mandatory for Croatian migrants, with diaspora resources being used both for fighting in the home country and campaigning in the host countries to seek support and recognition of the new state. Before the ascent of the Croatian Democratic Union (HDZ), the Croatian diaspora, which was already constituted as pro-independence by the time of Tito’s death in 1980, lacked a corresponding movement in the homeland and was unsuccessful in fueling conflict. Yet, during the escalatory phase of the conflict (1987–1991), Croatian emigrants largely intervened in the war for independence by providing strong financial assistance to Tudjman’s HDZ, which led the secession from Yugoslavia. Most diaspora funds were used to finance the political activities of the opposition, with whom the diaspora shared its willingness to oust the communist government and take concrete steps towards independence.9 2.5. Cuba Last, the Cuban case provides an interesting example of a diaspora whose attempts to ignite war in the origin country failed. After the revolution of 1959, important waves of emigrants fled the communist regime and settled down in the USA. Since then, the Cuban diaspora has been dominated organizationally by early migrants, who identified with the overthrown Batista dictatorship and remained strongly hostile to the revolutionary leaders. Although de facto unsuccessful at overthrowing Castro, the diaspora, through relentless lobbying activity, managed to keep Cuba at the top of the US foreign policy agenda and strongly affected the ability of the political regime in the homeland to carry on. In this respect, it can be noticed that whereas the dominant factions in the Cuban diaspora in the USA have maintained a highly conflictual approach to Castro’s Cuba, there are indications that younger generations, characterized by a more diverse and post-Cold War culture, are more supportive of a more pragmatic approach and would welcome a negotiated transition to democracy (Grugel and Kippin, 2007). 2.6. Further examples Beyene (2015) compares the roles of diasporas from Kenya, Nigeria and Ethiopia, which are known to send huge amounts of remittances to their (often conflict-plagued) home countries. He points out that the well-organized Kenyan diaspora is primarily involved in conflict resolution and peace-building affairs.10 On the opposite, migration from Ethiopia, mostly conflict-generated and in strong opposition with the government, appears to have had a peace-wrecking role and participated to the escalation of conflict.11 Somewhere between these two polar cases, the vast majority of Nigerian diaspora seems relatively inactive in conflict and political affairs in Nigeria. Other notable examples of migrants’ involvement in homeland conflict include communities as diverse and complex as the Armenian, Jewish, Kurdish, Albanian, Colombian or Cambodian diasporas. Overall, such cases are also extensively documented by an important literature in political sciences (see in particular Smith and Stares (2007), Roth (2015), Shain (2002), Pirkkalainen and Abdile (2009) and Koinova (2011)), and reproduce some of the features discussed in this section, thus adding up to the motivation of our research. 3. The model We start by presenting a simple model of conflict involving two rival groups. We are agnostic with respect to the source of difference between the two groups, which can be ethnic, religious, political, etc. As far as the benchmark version of the model is concerned, migration is assumed to be exogenous, and related to one group only. 3.1. The economic environment Total population is divided into two groups, indexed by E (the ‘elite’) and O (the ‘other’ group), respectively.12 Group E is made up of εE individuals, all residing in the homeland and characterized by productivity yE. Group O is originally made up of εO individuals. However, m members of this group migrate and live abroad. The εO – m resident members of group O have productivity yO, while the m migrants (who will be henceforth referred to as group M) are characterized by a productivity (1+μ)yO, with μ a strictly positive migration productivity premium. We further assume yE = κ yO = κy, with κ > 0, so that y can be interpreted as the overall level of development of the economy while κ is a measure of between-group inequality. In order to sidestep external effects and free-riding problems, we assume that each group’s decisions are taken by a leader who aims at maximizing the group’s average utility. As in Esteban and Ray (2008, 2011), individual utility is derived from private consumption c, and from a group-level public good Q which depends on the appropriation of a given resource (or public budget) R. The average utility functions maximized by the three group leaders are given by   uE=cE+χQE, (1)  uO=cO+χQO, (2) and   uM=cM+ηχQO, (3) where χ > 0 denotes the preference for the public good, which is further weighted by η > 0 in the case of migrants. Hereby we are suggesting that migrants are interested in the access of their group of origin to the public good, but may attach to it a different weight in their utility function.13 The quantity Qi (i = E, O) of public good that groups O and E can have access to depends on the appropriation of a contested resource R. Examples may range from the obtention of a (share of the) public budget highlighted by Esteban and Ray (2008, 2011), to sheer territorial expansion. The contested resource may be subject to violent conflict or shared through a process of negotiation. In case of conflict, group E (respectively, O) obtains a share s (respectively, 1 – s) of R, where s is given by the following contest function:   s(AE,AO)=γAEγAE+(1−γ)AO. (4) In the above expression, Ai (i = E, O) denotes the number of soldiers (or activists) that group i allocates to conflict and γ represents the relative (dis)advantage of group E in conflict.14 It reflects the idea that, prior to conflict, the two groups may have a different access to conflict-related information or technology, for instance.15 Alternatively, s(AE, AO) can be interpreted as the probability that group E will capture the whole amount of resource R. Open conflict is costly: it entrains the destruction of a share δ of the total resources located or produced in the economy, that is, residents’ private production (yO and yE) and R. Migrants differ from residents for they are not concerned by the destructive effect of war on private production. Conflict has also an opportunity cost: those who are employed as soldiers are removed from productive activities so that, for instance, group O gives up a total quantity of private consumption equal to AOcO. Such opportunity cost, however, cannot be directly affected by migration as long as we assume a constant marginal productivity of labor. Removing this assumption, in favor of decreasing marginal productivity, would imply that emigration, by reducing the size of the origin group, increases the wage of its members and, concomitantly, the opportunity cost of fighting. In this context, migrants can decide to get actively involved in the conflict by subsidizing soldiers from their group of origin (O).16 The value of the subsidy and the very fact that migration makes group O shrink are the two channels through which the diaspora interplays with conflict and the peace–war choice in our model. We rule out, however, that migrants can be recruited as soldiers, as well as the possible productivity and price effects of migration on the home economy.17 In case the two groups choose to split resources without resorting to armed conflict, they engage in a process of negotiation and must ultimately agree on the sharing rule s. Negotiation imposes a cost Z onto each group. Such a cost is justified by negotiation being time- or resource-consuming, and also accounts for the possibility that past conflicts generate hatred and distrust between the involved actors, thus making them, to some extent, prefer war over pacific settlement. A positive Z may also be related to the lack of a perfect commitment technology associated with the peaceful settlement of the conflict. 3.2. The model with conflict 3.2.1. Optimal choices Suppose now that R is contested through violent conflict. The leaders of the two resident groups E and O must determine the share of the labor force that they allocate to conflict, choosing θE and θO such that AE = θEεE and AO = θO(εO – m), respectively. On the other hand, the leader of group M decides a, that is, how much the diaspora will contribute for each soldier deployed by group O. This transfer may thus be interpreted as a subsidy to group O’s involvement in conflict. The total amount of war-targeted financial transfers, aAO, will then be shared equally among the resident members of group O, thus reducing the opportunity cost of war for group O. In our framework, production in the origin country is entirely transformed into private consumption. Accordingly, in case of war uE and uO write as   uE,w=(1−δ)((1−θE)κy+χs(AE,AO)R), (5) and   uO,w=(1−δ)((1−θO)y+aθO+χ(1−s(AE,AO))R), (6) respectively. Given that the utility function is linear in its two arguments, the convexity of the problem derives from the shape of the contest function. For a given a, the first order conditions ∂uE,w/∂θE=0 and ∂uO,w/∂θO=0 yield the reaction functions of the two groups, that is,   θE(θO)=γεE(1−γ)(εO−m)κyθOχR−κy(1−γ)(εO−m)θOκyγεE, (7) and   θO(θE)=γεE(1−γ)(εO−m)(y−a)θEχR−(y−a)γεEθE(y−a)(1−γ)(εO−m). (8) Figure 1 depicts the two reaction functions, as well as their intersection, which corresponds to the following equilibrium values:   θE*(a)=χR(1−γ)(εO−m)γεE(y−a)((y−a)γεE+κy(1−γ)(εO−m))2, (9)  θO*(a)=χR(1−γ)(εO−m)γεEκy((y−a)γεE+κy(1−γ)(εO−m))2. (10) Figure 1 View largeDownload slide Reaction functions of groups E and O. Figure 1 View largeDownload slide Reaction functions of groups E and O. The best-response functions are hump-shaped, meaning that when a group is faced with increasing opposition it initially responds by escalating conflict, but it is eventually limited by its resource constraint and decreases its involvement in conflict if the other group’s activism grows further. In case of complete symmetry ex ante and in the absence of active intervention by the diaspora (γ = 1/2, κ = 1, εE = εO – m, a = 0), the conflict equilibrium is also symmetric and lies on the 45° line. From θE*(a) and θO*(a) we can obtain AE*(a) and AO*(a), that is, the equilibrium sizes of the two armies, depending on a. As far as the diaspora is concerned, uM can be written, in case of conflict, as   uM,w=(1+μ)y−aθO*(a)(εO−m)m+(1−δ)ηχ(1−s(AE*(a),AO*(a)))R. (11) Knowing θE*(a), θO*(a), AE*(a) and AO*(a), the leader of group M maximizes uM,w with respect to a, the amount transferred to each soldier of group O. From ∂uM,w/∂a=0, we can retrieve a* as a function of m. It is possible to show that there exist m1 and m2 such that:   a*={0if m≤m1y(γεE+(1−γ)κ(εO−m))((1−δ)ηm−(εO−m))γεE((1−δ)ηm+(εO−m))if m1<m<m2y(γεE+(1−γ)κ(εO−m))−γεE(1−γ)(εO−m)κyχRγεEif m2≤m<εO. (12) If 0 < m ≤ m1, the optimization program of group M would lead to negative values for a*. Since the diaspora can only provide a non-negative contribution, we consider 0≤m≤m1 to be associated with the corner solution a* = 0.18 When m reaches m1, the diaspora becomes big enough for a strictly positive involvement in the conflict to be optimal. The size of this contribution increases with the number of migrants m.19 Finally, when m equals m2, the contribution of the diaspora is large enough to make θO reach one. In other words, group O’s involvement in conflict is so heavily subsidized by emigrants that all the resident members of group O are employed as soldiers (or activists), and payed out of the diaspora’s contribution. Overall, the function a*(m) behaves as represented in Figure 2. Figure 2 View largeDownload slide Equilibrium response of group M. Figure 2 View largeDownload slide Equilibrium response of group M. 3.2.2. Equilibrium We now turn to the analysis of the conflict equilibrium. By using the expression for a* in Equation (12) to replace a in Equations (9) and (10), we obtain the equilibrium values θE*, θO* and a* as functions of the parameters only. In order to have shorter expressions, we impose a few restrictions on the parameters. In particular, we set γ = 1/2 (symmetry in conflict between groups E and O), κ = 1 (groups O and E have the same productivity) and η = 1 (migrants value the public good as much as residents). We also assume that the parameters satisfy the following: Assumption 1 1−δ2<εEεO<1−δδ. This assumption, which is by no means necessary for the model to be solved but allows us to derive simpler results, requires the two groups not to be too different in size, so that none of them is big enough to push the other group out of conflict if its size marginally increases. Note also that the model can be fully solved in the general case of 0 < γ < 1, κ > 0 and η > 0 and would yield qualitatively similar results. Once the above assumption and parameter restrictions are taken into account, we can rewrite Equation (12) as:   a*(m)={0if m≤m1y(εE+(εO−m))((2−δ)m−εO)εE(εO−δm)if m1<m<m2y(εE+(εO−m))−εE(εO−m)yχRεEif m2≤m<εO (13) where   m1=εO2−δ, (14) while m2 solves θO*(a,m)=1.20 Although a* depends on several parameters, we use the notation a*(m) (as well as θE*(m) and θE*(m)) in order to highlight the impact of the diaspora size on the conflict equilibrium. By replacing a*(m) in θE*(a) and θO*(a), we further obtain:   θE*(m)={(εO−m)εEy(εE+(εO−m))2χRif m≤m1(εO−δm)(2εE+εO−m(2−δ))4y(εE+(εO−m))2χRif m1<m<m2εE(εO−m)yχR−yεE(εO−m)yεEif m2≤m<εO, (15) and   θO*(m)={(εO−m)εEy(εE+(εO−m))2χRif 0<m≤m1(εO+δm)2εE4y(εO−m)(εE+(εO−m))2χRif m1<m<m21if m2≤m<εO. (16) For ease of exposition, we call A, B and C the three regions defined by m≤m1, m1<m<m2 and m≥m2, respectively. The relationship between the diaspora’s contribution to conflict a* and its size m, for all admissible values of m, can be described as follows. Proposition 1 The value of the diaspora’s contribution at equilibrium, a*(m), is zero over region A. It is an increasing function of m over region B and a U-shaped function of m over region C.Proof. Follows from the inspection of the partial derivatives of the expression of a*(m) given by Equation (13). ▪ Looking at m1, we first can see that the minimal size at which the diaspora starts intervening actively in the conflict increases with εO and δ. If migrants come from a relatively small origin group, the size of the diaspora such that they start subsidizing conflict in the home country is also small. On the other hand, when a conflict is potentially more destructive (all other things being equal), the diaspora needs to reach a larger size before being interested in getting actively involved in the conflict. When the size of the diaspora is smaller than m1, there is no contribution from migrants. When m1 < m < m2, the diaspora intervenes actively in the conflict, and its contribution increases with its size. Finally, when m exceeds m2, the contribution of the diaspora ensures that θO remains constant and equal to 1.21 The following Proposition describes how the shares of workforce that, in equilibrium, the two groups allocate to conflict, depend on the size of the diaspora. Proposition 2 The relationship between the size of the diaspora and the shares of soldiers in each group depends on the shape of the diaspora’s contribution. In particular, over region A, θO*and θE*are ∩-shaped functions of m; over region B, θO*is a growing function of m while θE*is ∩-shaped; over region C, θO*is constant and θE*is a ∩-shaped function of m. Proof. Follows from the inspection of the partial derivatives of θE*(m) and θO*(m) as in Equations (15) and (16) with respect to m. ▪ Over region A, that is, as long as the diaspora does not subsidize conflict, groups O and E behave symmetrically and allocate the same share of their labor force to conflict. Each group’s θ* increases with the group’s size, as long as the latter is smaller than the other group’s size. However, if an already dominant group grows even bigger, both groups allocate a smaller share of their human resources to fighting. Within this region, although the diaspora does not contribute to the conflict, it influences it by its size. Namely, the share of soldiers in each group is a ∩-shaped function of m: when the number of migrants gets larger, group O becomes automatically weaker than group E in case of conflict, and must compensate by increasing its military engagement. Group E will react accordingly by increasing θE*. Eventually, however, if the diaspora grows further the pool of available soldiers becomes too small for group O to be able to prevail: group O will then withdraw human resources from conflict, causing group E to do the same. Within region B, the diaspora’s financial support to group O is internalized by both groups in their decision over the optimal share of soldiers. Different from region A (corner solution with ‘passive’ diaspora), the two groups do not have symmetric behaviors. In particular, the share of soldiers in group O always increases with the size of the diaspora. On the other hand, the impact of the diaspora’s support on θE*(m) is of ambiguous sign: it is positive when εE>(1−δ)m and negative when the inequality is reversed. When the diaspora is relatively small (with respect to group E), its financial involvement in conflict does not represent too big a threat for group E, which will simply adjust its θE* to match a larger a* and the implied increase in θO*. When the number of migrants is relatively large, the diaspora’s contribution to group O may act as a deterrent for group E, which prefers to reduce the number of its soldiers. Last, when m exceeds m2 (region C), the money sent back home by the diaspora is such that θO*=1. This region corresponds to another corner solution, in which the diaspora is active but, eventually, only affects the equilibrium via size effects since θO* is constant. Although interesting, the corner regions A and C are less informative regarding the interactions between diaspora and conflict. Within region A, the diaspora does not contribute financially to the conflict and only plays a role through a mechanical size effect. Region C sees group O invest all its human resources in conflict, regardless of the size of the diaspora. In what follows, we thus assume that the following holds. Assumption 2. The size of the diaspora is such that m1 < m < m2. This means that we focus on region B, where we observe simultaneously the size effect and the contribution effect of the diaspora. 3.3. War versus peace So far we have analyzed a situation of conflict, in which the two groups resort to war in order to ‘conquer’ their shares of the contestable resource R. However, this is not the only option available to the leaders of the two groups, who can alternatively sit at a table and peacefully negotiate how to share R. Negotiation implies that both parts agree on a sharing rule s, such that group E obtains fraction s of R, while fraction 1 – s goes to group O. Given the conflict-equilibrium value θi*(m) (i = E, O), the leader of group i may prefer to engage in a negotiation, which implies a fixed cost, rather than initiating conflict, which destroys resources and requires labor force. For this to be the case, there must exist a non-empty set of values of s such that the utility of group i in case of war, ui,w, is lower than its utility if a peaceful settlement is reached, ui,p. For negotiation to actually take place, there must exist values of s such that both groups are better off without war. Replacing a*, θE* and θO* into Equations (5) and (6), the utilities of the two groups in case of conflict can be rewritten as:   uE,w(m)=(1−δ)(y+(2εE+ε0−m(2−δ))2χR4(εE+(εO−m))2), (17) and   uO,w(m)=(1−δ)(y+(εO−δm)2χR4(εE+(εO−m))2). (18) Peaceful settlement avoids the destruction generated by conflict, and keeps all the labor force in the productive sector (θO and θE are set to zero). However, it implies that both groups pay a fixed cost Z. In case of peace, groups E and O thus obtain   uE,p=y+sχR−Z (19) and   uO,p=y+(1−s)χR−Z, (20) which, different from uE,w and uO,w do not depend on m. Solving ui,p = ui,w (for i = E, O), we can determine the threshold functions s˜E(m) and s˜O(m). These functions give the values of s which, for each possible m, make the two groups indifferent between open conflict and peaceful settlement. In particular, we obtain   s˜E(m)=Z−δyχR+(1−δ)((2εE+ε0−m(2−δ))24(εE+(εO−m))2), (21) and   s˜O(m)=1−(Z−δyχR+(1−δ)((εO−δm)24(εE+(εO−m))2)). (22) The two groups agree on a peaceful negotiation only if there exists a sharing rule s which makes both of them better off than war. It then follows that Proposition 3 For any given m, a pacific settlement is viable only if s˜E(m)≤s˜O(m). The negotiated sharing rule s is a priori undetermined, as there exist multiple values of s such that the two groups prefer peace to war. To resolve indeterminacy, we will assume later on (see Section 3.4) that in case of peace the sharing rule is the outcome of a Nash-bargaining process. Under Assumption 2, both functions s˜E(m) and s˜O(m) are decreasing with m. By subsidizing group O in case of conflict, a larger diaspora induces a higher propensity for group O to engage in conflict, while strengthening the preference of group E for a peaceful settlement. Otherwise said, a larger m strengthens the bargaining power of group O by increasing its conflict outcome uO,w. To assess whether the groups actually choose to negotiate peace, depending on m, we need to establish under which conditions s˜E(m) is smaller than s˜O(m). In case s˜E(m)>s˜O(m), no peaceful sharing rule would make both groups better off than war, which will then be the equilibrium. Switches between war and peace occur for values of m such that s˜E(m)=s˜O(m). Proposition 4 Let m^ and m¯ be the two values of m that solve s˜E(m)=s˜O(m), with m^<m¯. Under Assumption 2 (i.e. the diaspora’s contribution is positive but not large enough to push group O to employ all its members as soldiers), there exist   Z0=δy+14(1+δ)χR and   Z1=δy+χR(δ2+(2−δ)(1−δ)2εEεO((2−δ)εE+(1−δ)εO)2),with Z0 > Z1, such that: If Z > Z0, the diaspora cannot prevent war in the home country, that is, s˜E(m)>s˜O(m). If Z1 < Z < Z0, the two groups are at war for m = m1 and the diaspora is potentially peace-building. A switch from war to peace occurs within region B if m^<m2. A second switch from peace to war may also exist if m¯<m2. In such a case, an initially peace-building diaspora turns peace-wrecking as it becomes very large. If Z < Z1, the two groups are at peace for m = m1 and the diaspora is potentially peace-wrecking. A switch from peace to war occurs within region B if m¯<m2.Proof. Solving s˜E(m)=s˜O(m) yields the two possible solutions m^ and m¯, whose expressions are given in Appendix A. These solutions are real numbers only if Z < Z0. If Z > Z0, the two curves s˜E(m) and s˜O(m) do not cross, and s˜E(0)>s˜O(0). This proves (i). If Z < Z0, the two curves s˜E(m) and s˜O(m) intersect twice over ]−∞,∞[. Whether the two intersections m^ and m¯ fall within ]m1,m2[ determines possible switches from war to peace and peace to war. We also know that s˜E(m) and s˜O(m) are both decreasing functions of m over ]m1,m2[, but that there exists a value of m larger than m2 above which s˜E(m) starts increasing with m. This implies that m^ corresponds to a switch from war to peace, and that m¯ corresponds to a switch from peace to war. If Z1 < Z < Z0, m^>m1. This implies that s˜E(m1)>s˜O(m1) and the two groups are initially (i.e. at m = m1) at war. As soon as m reaches m^, s˜E(m) becomes smaller than s˜O(m) and the two groups prefer to peacefully share the contested resource. Peaceful negotiation effectively happens if m^ falls within the boundaries of region B, that is if m^<m2, and the diaspora then has a peace-building effect. Last, if m¯ also falls within the boundaries of region B ( m¯<m2), the diaspora can trigger a second switch from peace to war for large values of m. This proves (ii). Finally, if instead Z < Z1, then m^<m1 and the two groups are at peace when m = m1. However, if m¯ falls within region B, a growing diaspora is able to trigger a switch from peace to war, which proves (iii). ▪ Figures 3–5 describe the possible cases of non-neutral diaspora (i.e. when Z < Z0). The red (respectively, blue) line represents the threshold value of the sharing rule above (below) which group O (E) does not accept peaceful settlement. These lines are dashed in case of war, when the sharing rule derived from the conflict equilibrium is represented by the purple line. They are instead solid when the equilibrium is peaceful, that is, when s˜E(m)<s˜O(m), with the light green area representing the set of feasible sharing rules. Within this area, the solid green line depicts, for every possible m, the negotiated sharing rule derived from the Nash-bargaining process. Figure 3 View largeDownload slide Peace-building diaspora. Figure 3 View largeDownload slide Peace-building diaspora. Figure 4 View largeDownload slide Peace-building, then peace-wrecking diaspora. Figure 4 View largeDownload slide Peace-building, then peace-wrecking diaspora. Figure 5 View largeDownload slide Peace-wrecking diaspora. Figure 5 View largeDownload slide Peace-wrecking diaspora. In all cases, when m≤m1 (region A), s˜E(m) and s˜O(m) are both increasing with m. The diaspora does not contribute and only has a size effect on the equilibrium, making group E (O) more (less) willing to engage in conflict. Figure 3 describes the case of a peace-building diaspora (Z1 < Z < Z0). The two groups are at war when m = m1, and when m reaches m^, the diaspora is sufficiently large to trigger a switch to peace. Eventually, if m¯ is within region B, peace can be broken again when migration reaches this second threshold value. The diaspora then first plays as a peace-building actor, but turns peace-wrecking if its size becomes very large. Figure 4 illustrates this specific case. Last, Figure 5 describes the case of a peace-wrecking diaspora. The two groups are at peace when m = m1, which necessarily implies m^<m1<m¯. Peace prevails for every m smaller than m¯. When m eventually reaches m¯, the diaspora triggers a switch from peace to conflict. As stated by Proposition 4, the diaspora is neutral when the cost of peace is too high (Z > Z0), it has a peace-building potential when the cost of peace is relatively, but not prohibitively, high (Z1 < Z < Z0), and a peace-wrecking potential when the cost of peace is low (Z < Z1). In particular, a situation in which the diaspora, regardless of its size, has no chance whatsoever to pull the origin country out of war is more likely when Z0 is small. This corresponds to a relatively low cost of the war (low δy and/or low δχR). On the contrary, when the cost of the war is high (Z0 large), the diaspora is more likely to be able to play a role. If the diaspora is non-neutral (Z < Z0), it is more likely to play a peace-building role if Z1 is small. Looking at the effects of the parameters on Z1, the peace-building scenario becomes more likely if y, χ and R decrease. In fact, if a switching point exists, it will be from war to peace if s˜E(m1)>s˜O(m1), that is, the economy is at war when m = m1. This is more likely when the resources subject to potential destruction (y, R) as well as the importance of the contested resource in the utility function (χ) are limited. Finally, it may be interesting to look at the effect of the parameters on m^ and m¯, that is, the threshold size that the diaspora must reach in order to bring about a switch from war to peace and vice versa. The comparative statics on m^ and m¯ are not obvious because in general, they depend on specific conditions on the parameters. We can however prove the following results concerning the effects of the two groups’ size. Proposition 5 The threshold values m^ and m¯ increase with εE. They also increase with εO if εE < (1 – δ)m.Proof. The results can be established by applying the Implicit Function Theorem, under Assumption 1. ▪ The first result tells us that, as expected, it takes a larger diaspora to make the difference when the size of group E increases. In addition, the thresholds values increase with the size of group O only when group E is relatively small. This is due to the fact that the marginal impact of the diaspora on the origin group’s outcome decreases with the size of group E.22 3.4. Nash bargaining As mentioned above, if groups E and O decide to avoid war and resort to peaceful negotiation in order to split R, there can exist a set of values of s they may agree upon. To resolve such indeterminacy, we assume that the value of s which emerges is the outcome of Nash bargaining, that is   s(m)=arg max s(uO,p−uO,w(m))(uE,p−uE,w(m)). (23) In other words, the two groups maximize the product of their respective surpluses from peace (defined using war utilities as ‘threat points’).23 In particular, after replacing the conflict-equilibrium values θE*, θO* and a* in the utility functions, we obtain   s(m)={δ2+(1−δ)εEεE+εO−mif 0<m≤m1(2−δ)εE+εO−m(2−(2−δ)δ)2(εE+εO−m)if m1<m<m21−δ2−(1−δ)y(εO−m)y(εO−m)εEχRif m2≤m<εO. (24) It can be shown that the negotiated s is always increasing in m over regions A and C, while it decreases with m over region B under Assumption 1. This is due to the effect of m on the war outcomes of the two groups. As long as the diaspora does not subsidize conflict (region A), a larger m imposes a negative size effect on the share of resources that group O can obtain in case of war, thus weakening its bargaining power and leading to a higher s. A similar situation occurs in region C, where θO*=1: as group O shrinks, due to increased migration, its war outcome worsens and the share 1 – s of resources it can obtain through negotiation decreases. Instead, within region B, a larger diaspora translates into a potentially higher war outcome for group O, which can thus negotiate peace on better terms and impose a lower s on group E. 3.5. Back to the case studies Here, we try to bring back the results of our model to the case studies presented in Section 2. In particular, we argue that some of our theoretical findings are consistent with, and can be used to explain some distinctive features of the interaction of real-world diasporas with conflict in the origin country. In the case of Sri Lanka, we have seen that the political science literature emphasizes a major change in the attitude of the Tamil diaspora: in the aftermath of 9/11, with mounting international suspicion over the LTTE’s activity, diaspora members took some distance from their group of origin in the home country, loosened the links within their transnational networks, and increasingly supported a peaceful settlement. In the framework of the model, the evolution of the international environment can be thought of—from the viewpoint of the migrants’ group M—as an exogenous increase in the cost of subsidizing the war effort of group O. As a consequence, a*(m) becomes lower, thus contributing to the de-escalation of violence at home through a smaller θO*(m). An alternative interpretation would be that the increasing international attention on the transnational financing of armed groups implies a lower cost of peace (smaller Z), which in turn makes the diaspora less likely to fulfill its peace-wrecking potential.24 As far as the conflict in Northern Ireland is concerned, the involvement of the Irish-American community has undergone a clear evolution, from a strong support of armed struggle to a decisive peace-building role. Such evolution is traditionally explained with the transformation of the Irish-American community itself, which (i) evolved from a group of poor refugees and immigrants into a moneyed and highly networked community, well integrated in the American society, (ii) had its size eroded by demographic factors, namely smaller migration rates and (iii) became less tolerant of violence (and encountered more difficulties in funding political groups in Ireland) in the aftermath of 9/11. Our model can account for each of these mechanisms. In fact, a weaker adherence to the objective of the origin group (lower χ), a shrinking of the diaspora (lower m) driven by socio-demographic factors, and a lower cost of peace (lower Z) are all factors that can prevent a potentially peace-wrecking diaspora from igniting conflict at home. Also in the case of Somalia, our model can make sense of some specific features of the diaspora’s participation to conflict in the homeland. In particular, Somali migrants in different times—or different migrant groups—are known to have financed conflict in the home country in the hope of obtaining future benefits, and somehow gave up with the peace-building process since they had different stakes in conflict than the community of origin (which justifies the role and the consequences of χ and R in our model). The Somali case also provides a good justification for introducing a cost of peace Z, as modeled in Section 3. In fact, the peace-building effort of the diaspora was at times based on their willingness to finance compensational payments between fighting groups. Furthermore, we know from Section 2 that peace-wrecking diaspora remittances, which were intended to finance conflict and buy arms for the origin group, may have instead produced a peace-keeping effect by deterring violence from competing groups. This is fully consistent with our basic model (namely Section 3.3), where an arms race—possibly financed by migrants—prevents the outburst of conflict. Finally, the fact that Somali migrants were almost forced by clan leaders to finance the war effort of their origin groups provides some motivation for the extension presented in Appendix B, where we assume that the leader of group O controls the financial contribution of migrants.25 In a similar way, the presence of migrants from different groups in conflict in the Somali diaspora (and its consequent inability in determining the outcome of conflict in the home country) is captured by our extension with multiple sub-diasporas, developed in Section 5. Let us also stress that the presence of a large wave of pre-war, economic migration from Somalia, which played a substantial role in escalating conflict, somehow lends credibility to our benchmark setting with exogenous migration. The Croatian diaspora, which had peace-wrecking ‘intentions’, was initially unable to ignite a war for independence, essentially because it lacked local support in the homeland, but eventually became more effective during the second half of the 1980s. Our model suggests two possible explanations that are also compatible with historical evidence. First, the ascension of Milosevic to power in Serbia in 1987 led to a dramatic rise of nationalism. In our framework, this can be proxied by an increase in χ (the weight attached to the contested resource or public budget), which, as can be seen from Equations (15) and (16), translates into a higher intensity of conflict. Second, the substantial increase in Croatian migration during the 1980s may have helped the diaspora to bring about the transition towards war, which corresponds to a raise in m in Figure 5.26 Last, the case of Cuba, whose diaspora never managed to suscitate a counterrevolution in the homeland, can be interpreted, in terms of our model, as the diaspora failing to reach the threshold m¯ above which its involvement could have endangered peace (Figure 5). Recalling that this threshold depends positively on εE and negatively on εO as soon as εE is large (Proposition 5), it can be argued that the support that Castro had at home (large group E) or, alternatively, the virtually non-existent opposition inside the island while most of the opposition was abroad-living, prevented the diaspora from being actually peace-wrecking.27 4. Endogenous migration The model developed in Section 3 considers migration as exogenous. It may be argued, however, that migratory flows are not orthogonal to the existence of (a latent) conflict, and could result from the strategic choices of the two groups. To deal with this issue, we develop in this Section an extension of the benchmark model in which the leader of group O also chooses m so as to maximize the payoff of her group, taking into account that the resulting diaspora behaves as described by Section 3. This means that, although m is chosen by the leader of group O, the diaspora’s involvement in conflict, a, is decided by the leader of group M: once migrants are abroad, the leader of group O does not control their behavior anymore. In Appendix B, we will explore an alternative setting, in which the leader of group O controls both m and the possible transfers of resources between the diaspora and the homeland. In particular, the leader of group O chooses optimally both m and θO, taking into account that emigrants cannot become soldiers, and then equalizes utility across all group members, be they at home or abroad, by eventually transferring funds from the diaspora to the origin country. In this setting, the diaspora may thus be ‘forced’ to subsidize its origin’s group participation to conflict.28 4.1. The extended model: setup With respect to Section 3, we introduce two main changes. First, the objective function of the leader of group O modifies into   UO=εO−mεO(uO−Cm2εO)+ψmεO(uM−Cm2εO), (25) so that the leader of group O values a weighted average of stayers’ and migrants’ utilities (O and M, respectively). The weights result from the relative size of the two subgroups and the parameter ψ∈(0,1), which accounts for a form of altruism towards the diaspora. We also assume that migration is costly, and model this cost—which is shared by stayers and migrants—as a quadratic function of the number of migrants, with C > 0.29 Second, the decision process becomes more complex, since the leader of group O chooses m at a preliminary stage, before determining her conflict strategy θO. She, however, takes into account (but does not interfere with) the strategy of the diaspora, which chooses a independently as in Section 3. This alternative version of the model implies that, by choosing m = m*, the leader of group O also selects a war- or peace-equilibrium, deciding whether or not to exploit the peace-wrecking or peace-building potential of international migration. As there are now four variables—θO, θE, a and m—which must be endogenously determined, the problem becomes less tractable and we cannot provide analytical solutions for their equilibrium values. In order to illustrate the possible outcomes of the two-stage model, we then resort to numerical simulations.30 4.2. Numerical examples We now present a few numerical examples, based on parameter values that, although largely arbitrary, may have a plausible interpretation. We start by considering the case of a potentially peace-building diaspora, that is, a situation in which higher values of m may lead to a transition from war to peace. Different from the benchmark model (as summarized by Figure 3), here the leader of group O chooses m so as to maximize the objective specified in Equation (25). By selecting the optimal size of the diaspora m*, she also determines whether conflict erupts or remains latent in the shadow of negotiation. Consider Figure 6, which is based on the following parameterization: εE = 200, εO = 100, y = 2, κ = 1, R = 20, γ = 0.5, δ = 0.1, χ = 0.06, η = 1, μ = 2.1 and ψ = 1. In both panels, higher levels of m are associated to peace (the green-shaded area). The final outcome of the model, however, is different. The left panel depicts a situation (C = 0.024, Z = 0.43) in which the leader of group O maximizes her objective by selecting a relatively high value of m, which makes her prefer to engage in a peaceful negotiation over the contested resource. Instead, the economy represented in the right panel (C = 0.03, Z = 0.44) ends up in war. This numerical exercise highlights two possible factors affecting the choice between war and peace: along with Z (a higher cost of peace makes the size of the peace area shrink), the cost of migration C also plays a role. If migration has a peace-building potential, but is too costly, it may not fulfill its pacifying potential. Indeed, a higher C may render negotiation less attractive: when the diaspora becomes large enough to bring about a peaceful settlement, the payoff of peace is not big enough to compensate for the high total cost of migration. Figure 6 View largeDownload slide Endogenous m: peace-building migration. Figure 6 View largeDownload slide Endogenous m: peace-building migration. Figure 7 illustrates the symmetric case of a potentially peace-wrecking diaspora. Here, a higher cost of migration may preserve peace by pushing the leader of group O to send less group members abroad, thus preventing the diaspora from reaching the threshold size beyond which it precipitates the origin country in a civil war. The common parameters for the two panels of Figure 7 are εE = 200, εO = 400, y = 2, κ = 1, R = 20, γ = 0.5, δ = 0.1, χ = 0.06, η = 1, μ = 2.1 and ψ = 1. The left panel is built using Z = 0.525 and C = 0.008, while for the right hand side panel we set Z = 0.49 and C = 0.01: we can see how a higher cost of migration keeps the diaspora within the peace region, whose size is determined by Z in the usual fashion. Figure 7 View largeDownload slide Endogenous m: peace-wrecking migration. Figure 7 View largeDownload slide Endogenous m: peace-wrecking migration. 5. Migration from both groups Another possible limitation of the benchmark model developed in Section 3 is that it allows migration from one group only, namely O, while all the members of group E are supposed to remain in the home country. To deal with this issue, we present an extension with diasporas from both groups, which can get actively involved in the homeland conflict. Introducing a second diaspora from group E significantly complicates the analysis, and prevents us from going as far as in the benchmark model, in terms of analytical results. We will thus derive thereafter a few results about the mechanisms at play, which can be compared with the single-diaspora model, and then resort to numerical simulations in order to gain further insight about the implications of the model. 5.1. Model setup and optimal choices We denote by mO and aO (mE and aE) the exogenous size of the diaspora related to group O (E) and its financial contribution, that is, the subsidy it gives to each soldier employed by its group of origin. We make the same assumptions as in the benchmark specification, regarding both the resident groups’ and the diasporas’ utility functions. For simplicity, we also make the same simplifying assumptions on the parameters, namely γ = 1/2, κ = 1, and η = 1. The two groups now have symmetric utility functions that, in case of war, write as   uE,w=(1−δ)((1−θE)y+aEθE+χs(AE,AO)R), (26) and   uO,w=(1−δ)((1−θO)y+aOθO+χ(1−s(AE,AO))R), (27) respectively. For given aE and aO, we can retrieve from first order conditions the two groups’ reaction functions, whose intersection corresponds to the following optimal shares of soldiers:   θE*(aE,aO)=χR(εO−mO)(εE−mE)(y−aO)((y−aO)(εE−mE)+(y−aE)(εO−mO))2, (28)  θO*(aE,aO)=χR(εO−mO)(εE−mE)(y−aE)((y−aO)(εE−mE)+(y−aE)(εO−mO))2. (29) The expressions of θE*(aE,aO) and θO*(aE,aO) allow us to determine AE*(aE,aO) and AO*(aE,aO), which are taken into account in the diasporas’ programs. In case of conflict, the leaders of the diasporas decide aE and aO so as to maximize   uME,w=(1+μ)y−aEθE*(aE,aO)(εE−mE)mE+(1−δ)χs(AE*(aE,aO),AO*(aE,aO))R, (30) and   uMO,w=(1+μ)y−aOθO*(aE,aO)(εO−mO)mO+(1−δ)χ(1−s(AE*(aE,aO),AO*(aE,aO)))R, (31) respectively. As in the benchmark model, the optimal contribution of each group of migrants is a piecewise function of the diaspora size. In particular, there exist m1,E, m2,E, m1,O and m2,O such that: if mE ≤ m1,E (respectively, mO ≤ m1,O), aE* (respectively, aO*) is equal to zero; if m1,E < mE < m2,E (respectively, m1,O < mO < m2,O), aE* (respectively, aO*) is strictly positive; if m2,E ≤ mE < εE (respectively, m2,O ≤ mO < εO), all the resident members of group E (respectively, O) are employed as soldiers (and paid out of the diaspora’s contribution).31 Although we cannot determine analytically how aE* and aO*, and subsequently θE* and θO*, vary with mE and mO, we can identify five possible regions depending on the values of mO and mE: AA when mE ≤ m1,E and mO ≤ m1,O, none of the two diasporas decides to finance the involvement of its group of origin in conflict ( aE*=aO*=0); AB when mE ≤ m1,E and m1,O < mO < m2,O, or when mO≤m1,O and m1,E<mE<m2,E, only one of the two diasporas chooses to contribute ( aE*>aO*=0, or aO*>aE*=0); BB when m1,E < mE < m2,E and m1,O < mO < m2,O, both diasporas get financially involved in the conflict in the homeland ( aE*>0, aO*>0); BC when m1,E < mE < m2,E and m2,O ≤ mO < εO, or when m1,O < mO < m2,O and m2,E ≤ mE < εE, both diasporas contribute ( aE*>0, aO*>0), and one of the two groups of residents allocates all its labor force to conflict ( θE*<θO*=1, or θO*<θE*=1); CC when m2,E ≤ mE < εE and m2,O ≤ mO < εO, both diasporas contribute ( aE*>0, aO*>0) and both groups of residents allocate all their labor force to conflict ( θE*=θO*=1). For ease of exposition and in order to allow for comparison with the benchmark model, we now restrict our attention to region BB only. 5.2. War versus peace In case of war, the utility functions of groups E and O depend on mE and mO through the optimal values aE*, aO*, θE* and θO*, which are all endogenously determined at equilibrium. In case of peace, utilities are given by Equations (19) and (20) from Section 3. Solving ui,p = ui,w (for i = E, O) yields the new threshold functions s˜E(mE,mO) and s˜O(mE,mO), which give the values of s that make each group indifferent between conflict and peaceful negotiation.32 In order to understand how the existence of a second diaspora affects the peace or war outcome in the origin country, we simulate the behavior of the model and look at what happens when we let mE vary in the alternative cases of a peace-building and a peace-wrecking potential of the diaspora related to group O. These two scenarios are described in Figures 8 and 9, which can be regarded as the two-diaspora counterparts of Figures 3 and 5 in Section 3. Figure 8 View largeDownload slide Low versus high mE, when mO has a peace-building potential. Figure 8 View largeDownload slide Low versus high mE, when mO has a peace-building potential. Figure 9 View largeDownload slide Low versus high mE, when mO has a peace-wrecking potential. Figure 9 View largeDownload slide Low versus high mE, when mO has a peace-wrecking potential. Panels (a) and (b) of Figure 8 depict s˜E(mO) and s˜O(mO) for two different values of mE. We set εE = 500, εO = 400, y = 2, κ = 1, R = 20, γ = 0.5, δ = 0.1, χ = 0.065, η = 1 and Z = 0.525. This vector of parameters ensures that the diaspora of group O has a peace-building potential. In Figure 8(a), mE is set to 60, while we increase it to 120 in Figure 8(b). The simulations reveal that a larger mE increases the threshold value mO^ that triggers a switch from war to peace. Said differently, the existence of a larger diaspora emanating from group E makes it harder for the diaspora of group O to fulfill its peace-building potential. This is in line with the mechanism emphasized in the single-diaspora setting, namely that a diaspora makes its group of origin more willing to go to war, as its relative strike force is boosted by migrants’ contribution. Figure 9 generates the case of a potentially peace-wrecking diaspora by modifying the values of εE (namely, from 500 to 200) and χ (from 0.065 to 0.08). Again, we set mE equal to 60 in Figure 9(a), and 120 in Figure 9(b). A larger mE is associated with a higher threshold value m¯O, so that it becomes more difficult for the diaspora of group O to fulfill its peace-wrecking potential. Otherwise said, when the diaspora of group E is larger, it takes a larger migration from group O for its financial contribution to ignite conflict in the origin country. 5.3. Discussion To sum it up, extending the model to two diasporas allows us to draw a few reassuring conclusions regarding the robustness of our analysis. As far as the rival diaspora is not too large (region AA, where no diaspora subsidizes conflict, or AB, where only the diaspora from group O intervenes), the single-diaspora model leads to the same qualitative results as the two-diaspora extension.33 When the rival diaspora is larger and gets actively involved in the conflict (region BB), each diaspora attenuates the effect of the other, be it peace-building or peace-wrecking. Indeed, a diaspora makes its own group more willing to go to war and its rival group more willing to negotiate, and a rival diaspora has the opposite effects. Finally, consistent with Section 3, we do not delve into the analysis of very large diasporas (regions BC and CC), which would have the unrealistic effect of pushing the group of origin to employ all its members as soldiers. 6. Conclusion We propose a model of conflict to explore how a diaspora, by financially supporting its group of origin, may affect the intensity and likelihood of war in the homeland. We find that, if large enough, a diaspora is willing to contribute to the war effort of its group of origin. In case of actual conflict, this fuels the intensity of war, pushing the origin group to allocate a higher share of its members to fighting. However, the impact of the diaspora is not always peace-wrecking, as the strengthened bargaining power that it confers to its group of origin may deter the rival group from fighting and make the peace process more likely. In particular, we show that factors regulating the costs of war and peace in the home country determine whether the diaspora is more likely to act as a peace-building or peace-wrecking force. Although based on a few simplifying assumptions—namely, that migration is exogenous and concerns only one of the two resident groups—our benchmark model is rich enough to account for several aspects and determinants of the interaction between real-world diasporas and conflict in sending countries. When we extend the basic model so as to relax the above assumptions, we find that most of our main results carry through, thus showing that our theoretical framework is fairly general. In addition, we are able to obtain a few complementary findings related to the strategic management of migration by political leaders. As directions for further research, we would suggest considering complementary channels, both direct and indirect, through which the diaspora might affect conflict dynamics. In particular, the lobbying activity of diasporas might play an important direct role, in addition to the size effect and targeted remittances investigated here. As far as indirect channels are concerned, emigration may also shape the incentives to engage in conflict in the home country through non-targeted financial flows (i.e. private remittances), as well as productivity and price effects. For instance, in a setting with decreasing marginal productivity of labor, the diaspora may be more likely to have a peace-building role: by eroding the size of the origin group, emigration may in fact cause its productivity to increase, thereby raising the opportunity cost of conflict. Exploring these (and other related issues) would allow us to better gauge the importance of diasporas for the evolution and outcome of inter-group competition in the sending economy. Acknowledgements The authors are thankful to Fiona Adamson, José de Sousa, Frédéric Docquier, David Levine, Anna Lindley, Christopher McDowell, Alice Mesnard, Gerard Padro i Miquel, Hillel Rapoport, Dominic Rohner and Olivier Sterck for their comments on earlier drafts. The authors also thank the Editor and two anonymous referees for very helpful comments. The authors would like to express their gratitude to seminar participants at ULB (Brussels), IRES - UCLouvain (Louvain-la-Neuve), THEMA (Cergy-Pontoise), Dauphine (Paris), City University (London) and Sciences Po (Paris), as well as participants to the PET 2014 in Seattle, SMYE 2015 in Gent, CSAE 2015 conference on ‘Economic Development in Africa’ in Oxford, 2nd DIAL Development Conference in Paris, 2015 ASSET conference in Granada, IMI conference on ‘The Changing Face of Global Mobility’ in Oxford, 2016 International Conference on Migration and Development in Florence, 2016 EEA–ESEM Congress in Geneva, 28th SIEP Conference in Lecce and 7th Meeting of the Society for the Study of Economic Inequality (ECINEQ) in New York City, for useful and lively discussions. Funding Marion Mercier acknowledges financial support from the Marie Curie-Skłodowska Research Fellowship Program of the European Commission (H2020 Horizon), project MIGWAR, number 657861. This research is part of the ARC project 15/19-063 on ‘family transformations’ (French speaking community of Belgium). Footnotes 1 Horst (2008), among others, also reports such a variety of transnational political engagements, putting special emphasis on financial contributions. 2 Diasporas may also play a role for conflict in the host country, as it happened for the Palestinian diaspora in the context of the Lebanon war for instance. Discussing such cases remains, however, outside the scope of this article. 3 In reality, migrants also send funds to their origin country as remittances to their families. Private remittances are not neutral with respect to conflict, since they modify the recipients’ budget constraint and then their opportunity cost to get involved in civil war or become activists. Moreover, the existence of a conflict at home affects migrants’ propensity to remit (see in particular Carling et al. (2012) and Vargas-Silva (2016)). However, the analysis of the specific impact of private remittances on conflict is beyond the scope of this article. 4 Gunaratna (2003) estimates that the LTTE had an annual income close to 100 million dollars, of which the diaspora had contributed at least 60 million per year. 5 See, for instance, Arthur (1991); Adamson (2002); Horgan and Taylor (1999); Cox (1997). 6 The highly influential Irish Northern Aid Committee, also known as Noraid, was openly supportive of IRA’s armed struggle but progressively softened its stance. The 1990s saw the emergence of a new lobby group, the Americans for a New Irish Agenda (ANIA), which played a paramount role in lobbying the Clinton administration to promote a peace-building process in Northern Ireland. 7 Only older generations maintained a strong pro-war attitude. 8 The expertise and knowledge of diaspora members have been used to mediate in national reconciliation conferences and workshops around the country. In addition to their lobbying activities, diaspora members have also both formally and informally collected money to meet humanitarian and development needs. Diaspora Somalis have also been active in fueling and shaping the political debate at home (Menkhaus, 2006). 9 According to Hockenos (2003), more than 50 million dollars flowed from the diaspora toward the HDZ between 1991 and 1995, during the hot conflict stage. 10 More than 20 Kenyan diaspora-federated organizations, representing over 250,000 members, cooperate through the Kenya Diaspora Alliance (KDA), aiming at resolving conflicts at home and lobbying for a peace-building process. 11 The Eritrean diaspora intervened in the independence war mostly by providing funds for the armed struggle of the secessionist groups (Hockenos, 2003). 12 Group O can also be regarded as the ‘oppressed’ one, but this interpretation is not necessary. 13 Assuming that migrants are interested in the public good contested in the homeland is consistent with examples of diasporas being highly involved in the political situation in their home country, which may also be decisive for their opportunity to migrate back home. Although we do not explicitly model them, the determinants of η might be as diverse as the geographical distance between the origin and destination countries, the strength of migrants’ link with their group of origin (which may depend on whether they have family members back home), their willingness to return in the origin country, or the time they spent in migration. Intuitively, cultural assimilation and integration in the host country may also weaken the link with the source country. 14 Contest functions of this type, whose theoretical foundations are outlined in Jia et al. (2013) and Garfinkel and Skaperdas (2007), are widely used in the literature on conflict. 15 We do not assume γ larger or smaller than 1/2 so there is no prior on which group should have a relative advantage in the conflict. 16 Intervening or not in the conflict in the homeland can be a source of dispute among diaspora members, in the first place. We sidestep this issue, in order to focus on the interaction between the diaspora and the resident groups. 17 Considering that migrants cannot decide to migrate back in order to become soldiers is a simplifying assumption, which allows us to focus on the specificity of abroad-living actors involved into a distant conflict. Relaxing this assumption would significantly complicate the analysis, as the diaspora would have two variables to decide upon—namely its financial contribution and its human capital contribution. However, intuitively, this should yield qualitatively comparable results, since, in our setting, migrants’ financial contribution can only affect the intensity of war through the human resources which are dedicated to conflict. As far as residents and migrants have the same productivity in fighting, whether a soldier is a resident or a return migrant should not matter. 18 If we were to consider negative values for a, they could be interpreted as the diaspora withdrawing capital from the home country. 19 The equilibrium contribution is also a growing function of η, the parameter which captures diaspora members’ interest in the access of their group of origin to the contested resource. 20 The complete expression for m2, which is rather complicated, is given in Appendix A. 21 In this setting, an additional increase of the size of the diaspora has a U-shaped effect on the diaspora’s involvement. First, when the diaspora becomes bigger, the contribution is dissolved between more migrants which allows the subsidy a*(m) to diminish. At the same time, the shrink of the number of residents makes it more and more difficult to prevail in the conflict, and thus at one point the compensation from the diaspora which ensures that all the resident members remain soldiers needs to be bigger. 22 Recall that εE < (1 – δ)m also ensures that θE* increases with a* (see point (ii) of Proposition 2). 23 Note that the Nash-bargaining process we use is symmetric, as the two groups’ surpluses have the same weight in the objective. Asymmetry, however, may arise indirectly through the parameter γ, which affects the war outcomes of groups E and O. Here, the results are displayed under Assumption 1, and no such asymmetry is possible. 24 If the international community takes a stronger stance against the involvement of transnational networks in armed conflicts, this can take the form of increased police controls, which would increase the cost of conflict in sending countries, or high-level political activity intended to favor conflict resolution, which would actually decrease the cost of peace. 25 As stressed in Section 2, financial participation was also nearly mandatory for other groups of migrants, in particular the Croatian diaspora before independence, and Eritrean migrants who, after independence, were asked by the government to contribute 2% of their monthly income to the newly formed state (Fessehatzion, 2005); such contributions were not strictly compulsory, but largely perceived as a duty (Koser, 2007). 26 Notice also that the likelihood of the peace-wrecking scenario is in turn positively linked to increases in Z and χ, which can both be related to a surge in nationalism. 27 One may also speculate that Castro let the size of group O shrink substantially through migration, so as to minimize the risk of open conflict. 28 One could also think about migration as a fully decentralized decision taken by individual agents who compare, at any moment in time, utility at home and abroad. This (dynamic) extension of the basic model, which implies that both m and a are outside the influence of the leader of group O, is analyzed in the working paper version of this article (Mariani et al., 2017). 29 There can be multiple justifications for assuming an increasing marginal cost of emigration. We can think, for instance, to some form of congestion externality related to migration, decreasing returns to migrants’ labor, or that receiving countries take a stronger anti-immigration stance as m increases. 30 Some intermediate analytical results, such as the groups’ reaction functions and the characterization of different regimes, are available upon request. 31 The threshold values m1,E, m2,E, m1,O and m2,O are obtained following the same logic as Section 3.2.1, when determining Equation 12. In this extension, however, we must take into account that both migration and remittances are also allowed for group E, and influence the conflict equilibrium of the model. 32 We can further assume that the sharing rule negotiated by the two groups in case of peace is the outcome of a Nash-bargaining process, just as in the benchmark model. 33 The only difference being that, in region AB, the ‘passive’ diaspora triggers a size effect that, by weakening its group of origin, reinforces the role of the active one. References Adamson F. ( 2002) Mobilizing for the transformation of home: politicized identities and transnational practices. In Al-Ali N., Koser K. (eds) New Approaches to Migration? Transnational Communities and the Transformation of Home , pp. 155– 168. London: Routledge. Arthur P. ( 1991) Diasporan intervention in international affairs: Irish America as a case study. Diaspora: A Journal of Transnational Studies , 1: 143– 162. Google Scholar CrossRef Search ADS   Barsbai T., Rapoport H., Steinmayr A., Trebesch C. ( 2017) The effect of labor migration on the diffusion of democracy: evidence from a former Soviet Republic. American Economic Journal: Applied Economics , 9: 36– 69. Google Scholar CrossRef Search ADS   Batista C., Vicente P. C. ( 2011) Do migrants improve governance at home? Evidence from a voting experiment. The World Bank Economic Review , 25: 77– 104. Google Scholar CrossRef Search ADS   Beyene H. G. ( 2015) Are African diasporas development partners, peace-makers or spoilers? The case of Ethiopia, Kenya and Nigeria. Diaspora Studies , 8: 145– 161. Google Scholar CrossRef Search ADS   Blattman C., Miguel E. ( 2010) Civil war. Journal of Economic Literature , 48: 3– 57. Google Scholar CrossRef Search ADS   Brinkerhoff J. M. ( 2011) Diasporas and conflict societies: conflict entrepreneurs, competing interests, or contributors to stability and development? Conflict, Security and Development , 11: 115– 143. Google Scholar CrossRef Search ADS   Carling J., Erdal M. B., Horst C. ( 2012) How does conflict in migrants’ country of origin affect remittance-sending? Financial priorities and transnational obligations among Somalis and Pakistanis in Norway. International Migration Review , 46: 283– 309. Google Scholar CrossRef Search ADS   Chauvet L., Mercier M. ( 2014) Do return migrants transfer political norms to their origin country? Evidence from Mali. Journal of Comparative Economics , 42: 630– 651. Google Scholar CrossRef Search ADS   Cochrane F. ( 2007) Irish-America, the end of the IRA’s armed struggle and the utility of soft power. Journal of Peace Research , 44: 215– 231. Google Scholar CrossRef Search ADS   Collier P., Hoeffler A. ( 2004) Greed and grievance in civil war. Oxford Economic Papers , 56: 563– 595. Google Scholar CrossRef Search ADS   Constant A. F., Zimmermann K. F. ( 2016) Diaspora economics: new perspectives. International Journal of Manpower , 37: 1110– 1135. Google Scholar CrossRef Search ADS   Cox M. ( 1997) Bringing in the ‘international’: the IRA ceasefire and the end of the Cold War. International Affairs , 73: 671– 693. Google Scholar CrossRef Search ADS   Docquier F., Lodigiani E., Rapoport H., Schiff M. ( 2016) Emigration and democracy. Journal of Development Economics , 101: 1– 21. Docquier F., Rapoport H. ( 2003) Ethnic discrimination and the migration of skilled labor. Journal of Development Economics , 70: 159– 172. Google Scholar CrossRef Search ADS   Docquier F., Ruyssen I., Schiff M. ( 2017) International migration: pacifier or trigger for military conflicts? Journal of Development Studies , forthcoming. Esteban J., Ray D. ( 2008) On the salience of ethnic conflict. The American Economic Review , 98: 2185– 2202. Google Scholar CrossRef Search ADS   Esteban J., Ray D. ( 2011) A model of ethnic conflict. Journal of the European Economic Association , 9: 496– 521. Google Scholar CrossRef Search ADS   Fair C. C. ( 2007) The Sri Lankan Tamil diaspora: sustaining conflict and pushing for peace. In Smith H., Stares P. B. (eds) Diasporas in Conflict: Peace-Makers or Peace-Wreckers ? pp. 172– 195. Tokyo: United Nations Publications. Fessehatzion T. ( 2005) Eritrea’s remittance-based economy: conjectures and musings. Eritrean Studies Review  4: 165– 184. Garfinkel M. R., Skaperdas S. ( 2007) Economics of conflict: an overview. Handbook of Defense Economics , 2: 649– 709. Google Scholar CrossRef Search ADS   Grugel J., Kippin H. ( 2007) The Cuban diaspora. In Smith H., Stares P. B. (eds) Diasporas in Conflict: Peace-Makers or Peace-Wreckers ? pp. 153– 171. Tokyo: United Nations Publications. Gunaratna R. ( 2003) Sri Lanka: feeding the Tamil Tigers. In Ballentine K. (ed.) The Political Economy of Armed Conflict: Beyond Greed and Grievance, pp.  197– 223. Lynne Rienner Boulder, CO: Lynne Rienner. Hockenos P. ( 2003) Homeland Calling: Exile Patriotism and the Balkan Wars . Ithaca, NY: Cornell University Press. Horgan J., Taylor M. ( 1999) Playing the ‘Green Card’ – financing the provisional IRA: part 1. Terrorism and Political Violence , 11: 1– 38. Google Scholar CrossRef Search ADS   Horowitz D. L. ( 1985) Ethnic Groups in Conflict . Berkeley, CA: University of California Press. Horowitz D. L. ( 1998) Structure and strategy in ethnic conflict. In Pleskovic B., Stiglitz J. E. (eds) Annual World Bank Conference on Development Economics , pp. 345– 370. Washington, DC: World Bank. Horst C. ( 2008) The transnational political engagements of refugees: remittance sending practices amongst Somalis in Norway: analysis. Conflict, Security & Development , 8: 317– 339. Google Scholar CrossRef Search ADS   Jia H., Skaperdas S., Vaidya S. ( 2013) Contest functions: theoretical foundations and issues in estimation. International Journal of Industrial Organization  31: 211– 222. Google Scholar CrossRef Search ADS   Joshi M. ( 1996) On the razor’s edge: the liberation tigers of Tamil Eelam. Studies in Conflict and Terrorism , 19: 19– 42. Google Scholar CrossRef Search ADS   Koinova M. ( 2011) Diasporas and secessionist conflicts: the mobilization of the Armenian, Albanian and Chechen diasporas. Ethnic and Racial Studies , 34: 333– 356. Google Scholar CrossRef Search ADS   Koser K. ( 2007) African diasporas and post-conflict reconstruction: an Eritrean case study. In Smith H., Stares P. B. (eds) Diasporas in Conflict: Peace-Makers or Peace-Wreckers ? pp. 239– 252. Tokyo: United Nations Publications. Mariani F. ( 2007) Migration as an antidote to rent-seeking? Journal of Development Economics , 84: 609– 630. Google Scholar CrossRef Search ADS   Mariani F., Mercier M., Verdier Th. ( 2017) Diasporas and conflict. CEPR Discussion Paper 11926. Menkhaus K. ( 2006) The rise of Somalia as a Diaspora Nation: impact on peace-building, governance and development. Paper presented at the University for Peace Expert Forum on Capacity Building for Peace and Development: Roles of Diaspora. Toronto, Canada, October 19–20. Mohamoud A. A. ( 2006) African diaspora and post-conflict reconstruction in Africa. Copenhagen: Danish Institute for International Studies (DIIS). Orjuela C. ( 2008) Distant warriors, distant peace workers? Multiple diaspora roles in Sri Lanka’s violent conflict. Global Networks , 8: 436– 452. Google Scholar CrossRef Search ADS   Pfutze T. ( 2012) Does migration promote democratization? Evidence from the Mexican transition. Journal of Comparative Economics , 40: 159– 175. Google Scholar CrossRef Search ADS   Pirkkalainen P., Abdile M. ( 2009) The Diaspora-Conflict-Peace-Nexus: A Literature Review . Jyväskylä: University of Jyväskylä, Diaspeace Project. Preotu V. ( 2016) Emigration as a pacifying force? Geneva School of Economics and Management Working Paper 16033. Roth A. ( 2015) The role of diasporas in conflict. Journal of International Affairs , 68: 289. Shain Y. ( 2002) The role of diasporas in conflict perpetuation or resolution. SAIS Review of International Affairs , 22: 115– 144. Sheikh H., Healy S. ( 2009) Somalia’s Missing Million: The Somali Diaspora and Its Role in Development . New York: United Nations Development Programme. Skrbiš Z. ( 2000) Long-Distance Nationalism . Aldershot: Ashgate. Smith H., Stares P. B. ( 2007) Diasporas in Conflict: Peace-Makers or Peace-Wreckers?  Tokyo: United Nations Publications. Spilimbergo A. ( 2009) Democracy and foreign education. The American Economic Review , 99: 528– 543. Google Scholar CrossRef Search ADS   Van Hear N., Cohen R. ( 2017) Diasporas and conflict: distance, contiguity and spheres of engagement. Oxford Development Studies , 45: 171– 184. Google Scholar CrossRef Search ADS   Vargas-Silva C. ( 2016) Remittances sent to and from the forcibly displaced. Journal of Development Studies , 53: 1835– 1848. Google Scholar CrossRef Search ADS   Appendices A. Complementary results Here we report the analytical expressions for m2, m^ and m¯, referred to in Section 3, but omitted for ease of exposition. A.1. Expression for m2 in Section 3.2.2 The complete expression for m2, obtained solving θO*(a,m)=1, is   m2=−(4yεE)2−(δ2εEχR)2+8yεEδχR(2δεE−3(1−δ)εO)−Ω1/3(δ2εEχR+Ω2−4y(2εE+3εO))12yΩ1/3, (A.1) with   Ω=(4yεE)3+24y2εEχR(5(δεE)2−3εO(1−δ)(4δεE−3(1−δ)εO))−12y(εEχR)2δ3(2δεE−3(1−δ)εO)+(δ2εEχR)3+243yεE(εO−δ(εE+εO))yχR((4yεE)2−(δεE+9(1−δ)εO)2+54((1−δ)εO)2+(1−δ)δ3εEεO(χR)2). A.2. Expression for m^ and m¯ in Proposition 4 Solving ui,p = ui,w (for i = E, O) yields   m^=4(Z−δy)(εO+εE)−((3−δ)δεE+(1+δ)εO)χR−(εO−δ(εE+εO))(1−δ)ϕχR(1−δ)3χR−ϕ, (A.2) and   m¯=4(Z−δy)(εO+εE)−((3−δ)δεE+(1+δ)εO)χR+(εO−δ(εE+εO))(1−δ)ϕχR(1−δ)3χR−ϕ, (A.3) with ϕ=(1+δ)χR−4(Z−δy). B. Endogenous m: the ‘global social planner’ case Different from the benchmark model, here we consider a passive diaspora, whose size and involvement in conflict are both determined by the leader of its group of origin. In this sense, the leader of group O becomes a transnational social planner who centralizes all the decisions that are relevant for her group’s members, be they migrants or stayers. B.1. Setup We consider an economy with only two groups, O and E, where only members of group O can migrate. While the leader of group E behaves as in Section 3, that of group O must now decide simultaneously θO and m, thereby determining the size of the diaspora, which becomes an endogenous variable. In the same fashion as in Section 4, we introduce a quadratic cost of migration, so that the total cost of sending m members of group O abroad is given by Cm2. Different from Section 4, where the diaspora could autonomously decide its degree of participation to conflict in the origin country, we further assume that the leader of group O can redistribute resources across all group members in such a way that everybody enjoys the same level of utility. Therefore, in case of war, her objective becomes   uO,w=(εO−m)(1−θO)y(1−δ)+m(1+μ)y−Cm2εO+χ(1−s(AE,AO))(1−δ)R, (A.4) which can be compared with Equation (6) in the main text. In case of peace, we will instead have   uO,p=(εO−m)y+m(1+μ)y−Cm2εO+χ(1−s)R−Z, (A.5) which is the counterpart of Equation (20) in the benchmark model. As mentioned before, the objective functions of group E, uE,w and uE,p, are the same as in Section 3. B.2. Solving the model We can now solve the model along the lines of Section 4, that is, taking m as given. We then let the leader of group O select the value of m which maximizes her objective; by choosing m, she will implicitly choose between war and peace, very much in the spirit of Section 4.1. We start by finding the intersection of the two groups’ reaction functions, thus determining the equilibrium values of the θ’s in case of conflict, that is,   θE*(m)=χRγ(1−γ)εOεEy((1−γ)κεO+γεE)2, (A.6) and   θO*(m)=χRγ(1−γ)κεO2εEy(εO−m)((1−γ)κεO+γεE)2. (A.7) A first interesting result emerges: while θE* does not depend on m, θO* is increasing in m, which means that migration has an inherently peace-wrecking potential. From θE*(m) and θO*(m) we can obtain AE*(m) and AO*(m), that is, the equilibrium sizes of the two armies depending on m, as well as the utilities of the two groups in case of war. By comparing the war and peace outcomes of the two groups (i.e. solving ui,p = ui,w, for i = E, O), we are able to identify the threshold functions s˜E(m) and s˜O(m), which give the values of s such that, for each possible m, the two groups are indifferent between open conflict and peaceful settlement. In particular, after setting γ = 1/2, κ = 1 and η = 1 as in Section 3, we obtain   s˜E(m)=Z−δyχR+(1−δ)εE2(εE+εO)2, (A.8) and   s˜O(m)=−(εOZ−(εO−m)δy)εOχR+εE2+2εEεO+δεO2(εE+εO)2. (A.9) It can be seen that s˜E does not depend on m, while s˜O decreases in m. We can then claim the following. Proposition A.1 In the global social planner case, migration can only be peace-wrecking. In fact, if there is an intersection between the two threshold functions, s˜O(m) crosses s˜E(m) from above, meaning that there exists a value m¯′ of m, such that for any m>m¯′, war is the only possible outcome. Such peace-impeding level of migration is equal to   m¯′=εO(2(εE+εO)2(δy−Z)+(2εEεO+δ(εE2+εO2))χR)(εE+εO)2δy. (A.10) As far as the choice of m is concerned, the leader of group O will compare the possible utility she can reach under the two alternative scenarios of peace (i.e. for m≤m¯′) and war ( m>m¯′), and select m = m* so as to attain a global maximum of utility. Restricting our attention to interior solutions only (i.e. 0 < m* < εO), it can be shown that   m*={(δ+μ)y2Cif C<C^(δ+2μ)y4Cif C≥C^, (A.11) where   C^=(εE+εO)2(3δ+4μ)δy28εO(2(εE+εO)2(δy−Z)+(2εEεO+δ(εE2+εO2))χR). (A.12) This results lends itself to the following interpretation: if migration is not very costly, the leader of group O will try to exploit the peace-wrecking potential of migration and choose the size of the diaspora accordingly. If instead the cost of migration is high, the two groups will negotiate a peaceful sharing of the contested resource, a situation associated with a weaker migration outflow. © The Author(s) (2018). Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

Journal

Journal of Economic GeographyOxford University Press

Published: Mar 26, 2018

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off