Even highly correlated measures can add incrementally to predicting recidivism among sex offenders

Abstract

Criterion-referenced measures, such as those used in the assessment of crime and violence, prioritize predictive accuracy (discrimination) at the expense of construct validity. In this article, we compared the discrimination and incremental validity of three commonly used criterion-referenced measures for sex offenders (Rapid Risk Assessment for Sex Offence Recidivism [RRASOR], Static-99R, and Static-2002R). In a meta-analysis of 20 samples (n = 7,491), Static-99R and Static-2002R provided similar discrimination but outperformed the RRASOR in the prediction of sexual, violent, and any recidivism. Remarkably, despite large correlations between them (rs ranging from .70 to .92), these risk scales consistently added incremental validity to one another. The direction of the incremental effects, however, was not consistently positive. When controlling for the other measures, high scores on the RRASOR were associated with lower risk for violent and any recidivism. We also examined different methods of combining risk scales and found that the averaging approach produced better discrimination than choosing the highest score and produced better calibration than either choosing the lowest or highest risk score. The findings reinforce the importance of understanding the psychological content of criterion-referenced measures, even when the sole purpose is to predict a particular outcome and provide some direction concerning the best methods for combining risk scales.