Dissecting the Prevalence and Incidence of Offending During the Crime Drop of the 1990s

Abstract

To evaluate whether the 1990s crime drop reflects a decrease in offending prevalence (the fraction of the population engaged in crime), offending incidence (the frequency of offending among active criminals), or some combination of the two. We use individual-level longitudinal data on adolescent offending patterns from the Pittsburgh Youth study (PYS), integrating information from the youngest and oldest cohorts to compare offending among 17–18 year old males at the beginning and end of the 1990s. Logistic and negative binomial regression models are estimated to assess whether there are significant differences in offending prevalence and incidence during the 1990s. The reduction in property crime rates in the PYS sample during the 1990s can be attributed to declines in both offending prevalence and incidence. The overall decline in serious violence during the 1990s for the full sample was primarily the result of a falloff in prevalence. However, for black youth our results indicate significant reductions in both the prevalence and incidence of serious violence. We did not detect a significant difference in illegal drug sales during the period. Using longitudinal data on individuals to decompose aggregate crime trends into changes in the prevalence and incidence of offending offers insights into the nature of the 1990s crime drop that cannot be discerned from aggregate crime data. Future research should build on the current study by examining the specific mechanisms that influence change over time in crime prevalence, incidence, or both.