How many latent classes of delinquent/criminal careers? Results from mixed Poisson regression analyses

This article reviews questions about different categories of criminal careers, summarizes Poisson latent class regression models, describes procedures for evaluating the optimal number of latent classes, and applies this methodology to data from male cohorts taken from the cities of London, Philadelphia, and Racine. Four latent classes of offending careers is an appropriate number for the London cohort, but five classes can be justified for the Philadelphia data. In the case of the Racine cohorts, five classes may be detected for the 1942 and 1955 cohorts but only four for the 1949 cohort. Despite the varying numbers of latent offending classes, there clearly is a small number of typical age patterns.