Sexual Abuse: A Journal of Research and Treatment [saj] pp1003-sebu-474117 November 17, 2003 14:35 Style ﬁle version Nov 28th, 2002
Sexual Abuse: A Journal of Research and Treatment, Vol. 16, No. 1, January 2004 (
Stability of the Interpretative Risk Percentages
for the RRASOR and Static-99
Dennis M. Doren
Current procedures to estimate sex offender recidivism risk typically involve actu-
arial instruments, either alone or in combination with adjustments based on other
considerations. Two of the most commonly employed actuarial instruments for the
assessment of sexual recidivism risk are the Rapid Risk Assessment for Sex Of-
fender Recidivism (RRASOR; R. K. Hanson, 1997) and the Static-99 (R. K. Hanson
& D. Thornton, 2000). Although multiple studies of the interrater reliability and
predictive validity of these instruments have been completed, with very supportive
results, there have to date not been any studies of the degree to which the speciﬁc
risk percentages attached to each instrument’s score replicate and remain stable
despite changes in underlying samples’ recidivism base rates. This study, using
data from multiple sources, investigated this issue. The ﬁndings indicated that the
5-year risk percentages for the RRASOR were replicated and were remarkably
stable despite changes in the sample’s underlying recidivism base rate. The Static-
99 5-year risk percentages were mostly replicated and were stable across varying
base rates, but to a lesser degree than was found for the RRASOR. Implications of
these results are discussed.
KEY WORDS: RRASOR; Static-99; actuarial instrument; risk assessment; risk percentages.
Nearly 50 years ago, Meehl (1954) wrote a seminal paper describing the po-
tential improvement in predictive accuracy over clinical judgments through the use
of mechanical or actuarial assessments using research-determined considerations.
From the perspective that half a century has passed since that paper, it may be
“about time” that the use of actuarial instrumentation in assessing sex offender
recidivism risk has ﬁnally become commonplace, and research concerning the
accuracy of such devices is frequently found (Doren, 2002).
Sand Ridge Secure Treatment Center-Evaluation Unit, Madison, Wisconsin.
To whom correspondence should be addressed at Sand Ridge Evaluation Unit, 301 Troy Drive,
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2004 Plenum Publishing Corporation