An Improved Methodology for Analyzing Age-Arrest Profiles: Application to a Western Australian Offender Population

A new methodology for displaying and analyzing "arrest profiles" of a population of offenders is illustrated on a data set containing information on all arrests made in the jurisdiction of the state of Western Australia in the 12-year period 1 April 1984 to 31 December 1995. The arrest profile shows the number of arrests accumulated by an individual offender as a function of the age at which each arrest took place. This provides a summary of the "arrest careers" of the individuals in the population and facilitates comparisons between groups of interest in the population, such as sex and race groups. In particular, it enables comparisons to be made between cohorts of offenders defined by the age-at-onset of their offending. For the Western Australian population analyzed here we find large differences between sex and race (Aboriginal or non-Aboriginal) groups, and also between age-at-onset cohorts, and we place these differences in the context of current criminological discussions which posit that higher mean numbers of offenses will be committed by early career starters.