This report documents important and, in some cases, large effects of certain factors on reoffense and reimprisonment rates. These factors' effects must be accounted for when measuring and comparing recidivism rates. Failure to do so may bias recidivism measures and confound conclusions regarding whether differences in rates are attributable to certain correctional activities, functions, or programs. Evaluations using recidivism outcome measures for Florida state prison inmates should account for the following factors (or similar ones), measurable at the time an inmate is released:
Several aspects of the relationships between these factors and recidivism should be noted.
Not all factors affect recidivism with the same statistical significance. For males, 16 of 18 factors analyzed significantly influence reoffending and reimprisonment. For females, reoffending is significantly influenced by only 12 factors and reimprisonment by 10 factors. This variation in the effects of factors implies several conclusions.
A recent case from the research literature provides an example of problems caused by failing to account for the effect of an important factor that influences recidivism. A study published in 2002 on the relationship between education and recidivism (i.e., return to prison) of Oklahoma prison inmates (21,268 released from 1991 through 1994) found some unusual results. Among other findings, the study reported that: (1) earning a general equivalency diploma (GED) lowered recidivism, but that completing vocational training programs raised recidivism; (2) drug distribution offenses raised inmate recidivism, but drug possession offenses did not; and—most problematic—(3) older inmates recidivated at higher rates than younger inmates. However, there is scant theoretical reason to believe that vocational training actually increases recidivism. Further, most research shows inmates with drug possession offenses recidivate at rates at least equal to those with drug distribution offenses. Finally, virtually every study finds that younger inmates recidivate at higher rates than older inmates. The authors admit the odd findings may be due to the effect of repeat incarcerations, especially regarding the age finding, stating they "did not examine the effect of prior incarcerations." (See Brewster, Dennis R. and Sharp, Susan F. "Educational Programs and Recidivism in Oklahoma: Another Look" The Prison Journal, Vol. 82 No. 3, (September 2002) pp. 314-334.)
Had the authors of that research controlled for prior recidivism, a factor known to increase recidivism substantially, their results might well have been substantially different. Clearly, older inmates are more likely to have more prior recidivism events than younger inmates, so controlling for prior recidivism might have shown that older inmates recidivate less—a finding consistent with existing research. The Oklahoma Department of Corrections reports that drug possession inmates have a higher three-year recidivism rate (28.4%) than drug distribution inmates (23.5%), based on releases from 1985 through 1999; so controlling for prior recidivism could have allowed the authors to find results consistent with the agency's reports. More importantly, controlling for prior recidivism may have avoided the undesirable and theoretically problematic finding that vocational training increases recidivism, especially if vocational training completers in the sample were older and had more prior incarcerations. Finally, the desirable finding that earning a GED lowers recidivism would be credible, if the authors had not neglected to control for prior recidivism—a very important influence on recidivism.