Rev Ind Organ (2011) 39:3–18
Harm to Competition Under the 2010 Horizontal
Published online: 18 June 2011
© Springer Science+Business Media, LLC (outside the USA) 2011
Abstract In August, 2010, the Antitrust Division and the Federal Trade Commission
issued new Guidelines for assessing horizontal mergers under the antitrust laws. These
Guidelines were long awaited not merely because of the lengthy interval between them
and previous Guidelines but also because enforcement policy had drifted far from the
standards articulated in the previous Guidelines. The 2010 Guidelines are distinctive
manly for two things. One is briefer and less detailed treatment of market delineation.
The other is an expanded set of theories of harm that justify preventing mergers or
reversing mergers that have already occurred. The 2010 Guidelines reﬂect a growing
belief that in markets where product differentiation is minimal competition tends to be
robust and the structural presumptions stated in previous Guidelines were too harsh. By
contrast, where product differentiation is substantial the Guidelines’ approach tended
to deﬁne markets too broadly, overlooking significantly anticompetitive possibilities.
Under the 2010 Guidelines unilateral effects analysis relevant markets can be very
small, often limited to three or four ﬁrms, and excluding some obvious substitutes.
Markets in merger analysis are not deﬁned for their own sake, however, but rather to
ascertain whether a particular alteration in market structure covered by the merger pro-
visions will be likely to facilitate a price increase. The 2010 Guidelines address four
substantive merger concerns: exclusion, restraints on innovation, unilateral effects,
and coordinated effects. The Guidelines have a separate section on mergers limiting
“innovation and product variety,” treated mainly in the category of unilateral effects.
The 2010 Guidelines are more ﬂexible than previous Guidelines and also more catholic
about the types of harms that mergers might cause and the techniques that can be used
to assess them. Older Guidelines were excessively wed to methodologies that were
at the forefront of applied merger analysis when they were drafted, but that tended to
H. Hovenkamp (
College of Law, University of Iowa, Boyd Law Building, Iowa City, IA 52242, USA