Thirty years of research on the Level of Service Scales: A meta-analytic examination of predictive accuracy and sources of variability.

We conducted a comprehensive meta-analysis of the Level of Service (LS) scales, their predictive accuracy and group-based differences in risk/need, across 128 studies comprising 151 independent samples and a total of 137,931 offenders. Important potential moderators were examined including ethnicity, gender, LS scale variant, geographic region, and type of recidivism used to measure outcome. Results supported the predictive accuracy of the LS scales and their criminogenic need domains for general and violent recidivism overall, and among broad subgroups of interest, including females and ethnic minorities. Although results indicated that gender and ethnicity were not substantive sources of effect size variability, significant differences in effect size magnitude were found when analyses were conducted by geographic region. Canadian samples consistently demonstrated the largest effect sizes, followed by studies conducted outside North America, and then studies conducted in the United States. This pattern was observed irrespective of gender, ethnicity, LS domain, LS variant, or type of recidivism outcome, suggesting geographic region may be an important source of effect size variation. We discuss possible factors underlying this pattern of results and identify areas for future research.