Alfred Blumstein

The Criminal Career Paradigm

Criminal careers have long occupied the imaginations of criminologists. Since the 1986 publication of the National Academy of Sciences report on criminal careers and career criminals, a variety of theoretical, empirical, and policy issues have surfaced. Data on key criminal career dimensions of prevalence, frequency, specialization, and desistance have raised theoretical questions regarding the patterning of criminal activity over the life course. Recent research has identified important methodological issues, including the relationship between past and future criminal activity, and potential explanations for this relationship: state dependence and persistent heterogeneity. Advanced statistical techniques have been developed to address these challenges. Criminal career research has identified important policy issues such as individual prediction of offending frequency and career duration, and has shifted the focus toward the interplay between risk and protective factors.

On the Racial Disproportionality of United States' Prison Populations

One of the most distressing and troublesome aspects of the operation of the criminal justice system in the United States is the severe disproportionality between blacks and whites in the composition of prison populations. Although blacks comprise roughly one-eighth of the population, they represent about one-half of the prison population. Thus, the race-specific incarceration rates (the ratio of prisoners to population within each racial group) are grossly disproportionate. This disproportionality has been a source of major concern, largely because it suggests the possibility of gross injustice in the criminal justice system. The racial differences in imprisonment are reflected in Table 1, which presents demographic-specific incarceration rates (in units of prisoners per 100,000 persons within each indicated demographic group) in state prisons (not including federal prisons or local jails) for blacks and whites and their total.1 This table highlights the great sensitivity of in-

Characterizing Criminal Careers

Most knowledge about crime and criminals derives from cross-sectional analyses that link crime rates in a community with a communitys attributes. The criminal-career approach focuses on individual offenders and considers their crime-committing patterns as a longitudinal stochastic process. This approach, which invokes parameters characterizing participation rate, initiation rate, termination rate and the associated career length, and individual offending frequency, offers some important new insights. For example, annual offending frequency appears to be reasonably constant with age for those offenders who stay criminally active, termination rates are relatively low for active offenders in their 30s, and offending frequencies seem to be relatively insensitive to demographic attributes for active offenders. All these observations are opposite to those that would be derived from cross-sectional analysis.

Assessing the Impact of Exposure Time and Incapacitation on Longitudinal Trajectories of Criminal Offending

The authors examine the potential effect of accounting for exposure time by examining the arrests of 272 serious offenders who were paroled at age 18 and followed through age 33. The authors describe the overall change in the arrest rate over the 16-year period, with and without adjustments for exposure time. The authors also estimate latent class models that decompose the heterogeneity of arrest rate trends, with and without variation in exposure time. Two results are noteworthy: (a) conclusions about the level of arrest activity did depend on adjustments for exposure time, but the overall trend in arrest activity did not depend on these adjustments; and (b) latent class analysis without exposure time adjustments suggested that more than 92% of the sample exhibited their highest level of arrest activity in late teens and early 20s; then offending declined during the late 20s and early 30s. When adjusted for exposure time, the analysis revealed that about 72% of the sample exhibited this decline; the remainder remained quite active in offending.

Delinquency Careers: Innocents, Desisters, and Persisters

The Philadelphia birth cohort studys finding that 6 percent of the boys born in Philadelphia in 1945 experienced 52 percent of the cohorts arrests stimulated a variety of research and policy initiatives including, recently, those relating to selective incapacitation. Results from three other longitudinal delinquency studies-from London; Racine, Wisconsin; and Marion County, Oregon-parallel those of the Philadelphia study. A high percentage, typically at least one-third, of cohort members are arrested or convicted. Of these, many have only one or a small number of official contacts with the criminal justice system. A small percentage have six or more contacts, and for these the probability of subsequent recidivism, after any contact, is approximately 80 percent. The prospective identification of these chronic offenders could have significant crime reduction impact. Most incapacitation research has, however, involved retrospective, not prospective, identification of chronic offenders and has been characterized by high false positive rates. The London study, by contrast, identified seven variables that are apparent by age ten (such as IQ, family background factors, and behavior problems in school) and that may permit prospective identification of a substantial number of chronic offenders. The prediction results closely match the results of predictions based on a theoretical model that uses aggregate recidivism data to partition a cohort into three groups: innocents, who have no offending record, desisters, who have a low recidivism probability, and persisters, who have a high recidivism probability. The results suggest the possibility of early discrimination between more and less serious offenders and also support the view that the rise in recidivism probability with increasing involvement in crime results from a changing mix of desisters and persisters among the offenders.

Population Growth in U. S. Prisons, 1980-1996

State and federal incarceration rates grew by over 200 percent between 1980 and 1996. The dominant factor is drug offending, which grew by ten times, followed by assault and sexual assault. The growth can be partitioned among four stages: offending rates; arrests per offense; commitments to prison per arrest; and time served in prison, including time served on parole recommitments. The growth in incarceration for drugs is driven most strongly by growth in arrest rates, then by commitments per arrest; there is some increase in time served, but only in the federal system. For other offenses, there are no changes in arrests per reported offense and a net decline in offending rates. Over the full period, the growth in state incarceration for nondrug offenses is attributable entirely to sentencing increases: 42 percent to commitments per arrest and 58 percent to time-served increases. Recently, new court commitments and parole violations have flattened out; the dominant contributor to current growth for all the offenses examined is time served. Incarceration rates rose faster for women (364 percent) and minorities (184 percent for African Americans and 235 percent for Hispanics) than for men (195 percent) and non-Hispanic whites (164 percent).

Specialization and Seriousness During Adult Criminal Careers

Crime-type switching between arrests is examined for tendencies by adult offenders to specialize in crime types or to escalate in seriousness as offending continues. The adult offenders examined display higher levels of specialization than have been previously reported for juveniles; among adult offenders, those who remain criminally active until older ages are also more specialized. Also, there is some evidence of trends toward a worsening of offending: for selected crime types, adult offending becomes more specialized and escalates in seriousness for white offenders. However, similar trends are not observed for black adult offenders.

Linking gun availability to youth gun violence

In the United States, opinion polls over the last several years have consistently placed violence near the top of the publics list of concerns. This seems to happen regardless of whether homicide rates are climbing or falling. In this paper, we examine the time trends in homicide rates in the United States, and find that the fears are not totally inappropriate, even in the recent years when homicide rates have been falling. We find that, while there has been a significant decline in homicides committed by older offenders, homicides committed by younger offenders grew dramatically beginning in 1985. An important factor in that growth has been a significant increase in the availability of guns to young people. By examining time trends in age-specific arrest rates for homicide (gun homicide compared to non-gun homicide) and similar trends in drug-related arrest rates (juveniles compared to adults), the role of gun availability, especially as it has risen through the recruitment of young people into drug markets, is identified as a probable cause of these homicide trends. Further examination of mortality rates-due to gun homicides compared to non- gun homicides as well as gun suicides compared to non-gun suicides-for various age and race groups also implicates gun availability as a key contributing factor to the growth in youth homicide.

Demographically disaggregated projections of prison populations

Abstract The need for improved long-run projections of prison populations has increased in recent years because of record-high numbers of inmates and severe overcrowding in state and federal prisons, and because of the growing importance of changing demographic factors in influencing corrections populations. A model is developed for projecting: general population demographics; demographic- and offense-specific arrest rates, imprisonment probabilities, and times served; and then the size and composition of prison populations. Model parameters are estimated for Pennsylvania and are shown to be sensitive to demographic factors, particularly age and race. Projections of future arrests, prison commitments, and prison population are developed for Pennsylvania using projections of demographic changes in the states population. Arrests are expected to peak in 1980, prison commitments are expected to peak in 1985, and prison populations are expected to peak in 1990, with the subsequent declines reflecting the maturation of the postwar baby boom children out of the highly crime-prone ages and, somewhat later, out of the highly prison-prone ages.

PREVALENCE AND RECIDIVISM IN INDEX ARRESTS: A FEEDBACK MODEL

It is important for both theoretical and policy reasons to partition aggregate crime rates into measures of prevalence (reflecting breadth of participation) and incidence (reflecting intensity of participation by those who do engage in crime). Prevalence is measured by accumulating over age the probability of first arrest as a function of age. Incidence is estimated by the probability of recidivism in a feedback model. The probability of a male in U.S. cities over 250,000 population ever being arrested for an index crime is estimated as 25 percent, and is quite different for black males (51 percent) and white males (14 percent). The probability of re-arrest for an index crime is estimated as 85 to 90 percent for both whites and blacks. These estimates highlight the breadth of involvement in index-crime arrests, and suggest that the large differences in race-specific arrest rates are predominantly attributable to difference in participation, and not to differences in recidivism for those who do get involved.