small group of incarcerated offenders could, in the absence of imprisonment, substantially increase the violent crime rate.

Typically the incapacitation effect (I) of imprisonment is measured on a percentage basis by comparing the number of crimes that are prevented by incapacitation to the total number of crimes that would have been committed if offenders were fortunate enough to avoid imprisonment. Thus, I for violent offenses depends fundamentally on the number of crimes that incarcerated offenders would commit if they were to remain free in the community, which in turn rests on the mix of offense types that offenders commit, individual rates of committing violent crimes while offenders are free, and the length of time that offenders will continue to commit violent crimes.²⁶ Assessing the crime control effects of incapacitation in reducing violent crimes thus requires that we inquire about the general characteristics of offending careers and the role of violent offenses in those careers.

Although studies that focus exclusively on violent offenders are rare,²⁷ empirical evidence about violent offending can be found in cross-sectional and longitudinal studies of general offending careers. The bulk of this literature, as it applies to violent crimes, has been reviewed by Farrington (1982), Blumstein et al. (1986), and more recently Weiner (1989). We discuss briefly the empirical findings about the contributions of violent offenses in offending careers and highlight their implications for incapacitation. The results from this research generally support the conclusion that incapacitation has nontrivial consequences for the control of violent crime.

At the end of the section, we offer estimates of I for robbery in California, Michigan, and Texas. These estimates were computed based on a model that explicitly incorporates important features of the crime-generating process previously observed in empirical research. Comparable estimates for other violent offenses remain unavailable at this time.

Violent offenses constitute a relatively small percentage of the total crimes generated by an offender population. For example, Tracy et al. (1990) found that violent offenses represented less than 5 percent of total police contacts in cohort studies of juvenile offending by Philadelphia boys born in 1945 and 1958. Similar results were reported by Shannon (1982, 1988) for each of three birth cohorts traced in Racine, Wisconsin. In summarizing

Front Matter (R1-R8)

Public Perceptions and Reactions to Violent Offending and Victimization (1-66)

The Costs and Consequences of Violent Behavior in the United States (67-166)

Violence and Intentional Injuries: Criminal Justice and Public Health Perspectives on an Urgent National Problem (167-216)

Predicting Violent Behavior and Classifying Violent Offenders (217-295)

Incarceration and Violent Crime: 1965-1988 (296-388)

Index (389-397)