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AGE, CRIMINAL CAREERS, AND POPULATION HETEROGENEITY: SPECIFICATION AND ESTIMATION OF A NONPARAMETRIC, MIXED POISSON MODEL

NCJ Number
144630
Journal
Criminology Volume: 31 Issue: 3 Dated: (August 1993) Pages: 327-362
Author(s)
D S Nagin; K C Land
Date Published
1993
Length
36 pages
Annotation
This article examines whether, during the life course, individual offending patterns are marked by periods of quiescence, whether such patterns vary systematically with age, and whether chronic offenders are different from less active offenders.
Abstract
The authors analyzed data tracking 403 males from age 10 to 32. (Data for eight others who died during the observation period were not included.) The subjects themselves, relatives, and friends were interviewed regarding psychological characteristics as well as socialization and family background variables. Among the 36 percent of respondents who had at least one conviction during the period, the average number of convictions was 4.4. Convictions rose steeply and reached a peak during the time block of age 16 to 19, then declined steadily; thus, the authors conclude that the age trajectory is single- peaked, rather than flat. The authors, used a mixed Poisson (governed by a mean offense rate parameter) model to incorporate observable individual characteristics and unobservable heterogeneity among individuals. Consequently, they observed that the average offense rate varies according to a synthesis of these factors. They then categorized the subjects into four distinct classes: nonoffenders, high-rate chronics, adolescent-limited, and low-rate chronics. They discussed psychological, family, and social variables as applied to each offender class and age group. Overall, some findings supported the criminal propensity (latent trait) theory although others favored the conventional criminal careers theory; criminal career models that account for inactive periods are superior to those that do not. 8 tables, 3 figures, 2 appendixes, 18 footnotes, and 39 references