Factors Affecting Recidivism Rates

Scientific studies have documented that many factors contribute to recidivism rates. These include such personal characteristics as age, gender, race, length and severity of criminal history, education and skill levels, and conduct in prison. Other factors such as length of incarceration are believed to affect recidivism rates as well.

For public safety reasons, the public and policymakers routinely consider recidivism rates an important-if not paramount-measure of the corrections system's performance. Therefore, it is necessary to know how these factors affect recidivism rates so they can serve as a correct benchmark for measuring whether and how well policies or programs expected to reduce recidivism actually work.

This report does not evaluate the Department's performance based on recidivism rates. Instead, the report provides a proper context for understanding the results of evaluations that use recidivism rates to assess the Department's performance.

Combined Effect of Factors on Recidivism Rates

This study only includes factors for which the Department has data at the time an inmate is released from prison. This data is reliable, readily available, and should remain so over time. Among the factors analyzed, the following nine factors are significantly related to recidivism: age at release, prior recidivism, race, gender, education level, offense type, custody level at release, number of disciplinary reports received, and time served in prison. Available data is not sufficient to analyze post-release factors such as employment, drug and alcohol use, and the extent of formal and informal supervision which may also affect recidivism rates.

A good way to understand how much these factors, as a group, affect recidivism is to test how well they predict whether inmates recidivate at certain times after release. A standard cross validation technique was used to measure the predictive value of a statistical model incorporating these nine factors. The model was tested at three follow-up periods to ensure that its predictive value does not vary unacceptably across follow-up intervals. Knowing these nine factors our ability to predict whether or not an inmate would recidivate was improved as follows:

• 19.0% at 18 months after release
• 22.8% at 36 months after release
• 22.0% at 60 months after release.

For more information on the statistical procedure used to evaluate this prediction model see the Technical Appendix.

	18 Months After Release	36 Months After Release	60 Months After Release
Prediction Sample Size	43,877	36,010	27,683
Validation Sample Size	44,040	35,929	27,821
Errors Expected by Chance	19,433	17,941	10,949
Correct Predictions Expected	24,607	17,988	16,872
Prediction Errors by Model	14,769	13,839	7,238
Correct Predictions by Model	29,271	22,090	20,583
Expected Percent Correct	55.9%	50.1%	60.6%
Actual Percent Correct	66.5%	61.5%	74.0%
Prediction Improvement	19.0%	22.8%	22.0%

Recidivism Charts and Tables for Factors

These charts demonstrate how much each of the factors, other than the year released, influence recidivism rates. Each curve chart shows the relationship between a factor or factors and recidivism rates over time. Actual recidivism rates for each chart appear in the associated table. The table provides data for selected follow-up periods from six months to six years after prison release. For an explanation of how to interpret these charts see Recidivism Rate Curves.

The Relative Influence of Factors on Recidivism Rates

The factors above are listed in order of their relative influence on recidivism rates for inmates released from our facilities, beginning with the most influential: age at release. The relative effect of these factors was determined using a statistical procedure (proportional hazards regression) that analyzes their respective effects on recidivism simultaneously. This allows us to know three things about these factors:

• whether a factor has a statistically significant effect on recidivism,
• whether one factor accounts for more variation in recidivism rates than others,
• whether and by how much each factor tends to raise or lower recidivism rates.

For more information on the methodology and statistical procedure used to measure these factors' relative influence on recidivism see the Technical Appendix.

• On average, an inmate's probability of reoffending drops by 2.1% for each year older the inmate is at release.
• Younger offenders reoffend at much higher rates than older offenders.

On average, inmates who have recidivated at least once before are 58.1% more likely to reoffend than those who have not. For prison releases since 1993, inmates who recidivated previously do so again at higher rates than those without a prior recidivism event.

On average, black inmates are 43.6% more likely to reoffend than non-blacks. On average, male inmates are 24.2% more likely to reoffend than females. Black males appear to recidivate at higher rates than white males. Some factor other than race may account for much of the difference between black and white male offenders' recidivism rates because the race difference is larger for males than for females.

On average, an inmate's probability of reoffending drops by 2.9% for each higher grade of adult basic education tested. Education grade level tests are given to all offenders entering prison. Test results are available whether or not an inmate received education programming in prison.

On average, released inmates whose primary offense is a property offense are 13.9% more likely to reoffend than others. On average, released inmates whose primary offense is a violent offense are 31.9% less likely to reoffend than others. Property offenders recidivate slightly more than drug offenders. Both groups recidivate much more than offenders imprisoned for violent offenses.

On average, inmates released directly from close custody are 10.8% more likely to reoffend than others. Those released from medium and minimum custody recidivate at similar rates after release. The higher recidivism rates for close custody releases may result from some other underlying factor, such as limited participation in some kinds of programming while in close custody or because those still in close custody at release are more violent and disruptive individuals.

On average, an inmate's probability of reoffending rises by 1.6% for each additional disciplinary report received while in prison. This suggests that inmates who break the rules more often while in prison are more likely to do so after release than those inmates who abide by the rules while in prison.

On average, an inmate's probability of reoffending drops by 1.2% for each additional year spent in prison. The somewhat lower recidivism rate for inmates who spent more than five years in prison may appear because this group contains a higher percentage of older inmates, who reoffend less than younger inmates.

Recidivism rates do not vary much for inmates released during different fiscal years (July - June). The shape of the recidivism rate curves are similar for inmates released each year. Since recidivism rates are not changing much from year to year they may have limited value as annual performance measures.