Results: Adult Males

Table 4 presents the base recidivism rates using the re-offense measure generated from the SAS© lifetest procedure described earlier with follow-up periods of six months to sixty months. These data show that, in the short term through an eighteen months follow-up period, the re-offense rates of public and private adult male inmates are virtually identical within all six of the outcome measures. In the longer follow-up periods of thirty-six months and sixty months, private adult male inmates have higher re-offense rates within four of the six groups (A1, B1, B2, and B3) and are the same as the public adult male inmates in the A2 and C1 groups. However, none of these re-offense rate differences are statistically significant at the p<.05 level.

Re-imprisonment rates are displayed in Table 5, prior to controlling for relevant factors, for the public and private adult male releases within each of the six methods of identifying the two types of inmates. Overall, public adult male inmates have slightly higher re-imprisonment rates; however, only four of the possible thirty-six differences are higher than 2.0% (Groups A2 and C1 for thirty-six months, Group A2 for 48 months, and Group A1 for 56 months) and none are over 3.0%. Additionally, none of these re-imprisonment rate differences between public and private adult male inmates are statistically significant at the p<.05 level.

Table 6 displays the distributions of the private and public adult male inmates on the eighteen variables used in the final survival models to answer the question whether recidivism rates differ between the two groups. The demographic characteristics of age at release, race, and ethnicity, across the public and private adult male inmates are virtually the same. In contrast, public adult male inmates are somewhat more likely to have more prior recidivism events than private inmates (average: public = 1.2; private = 1.1) and are considerably more likely to be released as close custody inmates (public = 17.0%; private = 1.1%). Public adult male inmates are also much more likely to spend longer lengths of time in prison (average months: public = 31.3; private = 16.8) and have more disciplinary problems while in prison (average disciplinary reports: public = 2.9; private = 0.8). The median TABE score for public adult male inmates is slightly lower than for private adult male inmates (7.1 versus 7.6) and they are considerably more likely to be released to some form of post-prison supervision (36.9% versus 23.4%). In terms of their most serious crime type, public adult male inmates are more likely to have committed a homicide, sex/lewd offense, or a robbery than private inmates. However, the two groups are very similar in terms of their total number of convictions for property, drug, and weapons offenses.

The differences described on many of the control variables for the public and private adult male inmates clearly indicates the need to hold these factors constant when evaluating whether differences in recidivism probabilities exist between the two groups. Public adult male inmates have higher rates of prior recidivism rates, close custody, and disciplinary infractions, as well as lower TABE scores. These characteristics are all associated with a higher likelihood of recidivism. In contrast, private adult male inmates have shorter lengths of stay in prison and are less likely to have post-prison supervision, which are predictive of higher recidivism rates.

To determine whether the private prison experience for adult males affects their likelihood of recidivism in terms of re-offense or re-imprisonment rates, we employed multivariate survival models which control, or hold constant, the effects of other variables known to influence recidivism rates. Table 7 displays these results and clearly shows there are no statistically significant differences in re-offense or re-imprisonment rates between public and private adult male inmates using any of six methods for quantifying private prison experience. Using the re-offense recidivism measure, all the relationships between the type of prison and reoffense indicate that private inmates are slightly more likely to recidivate than public adult male inmates (MLE’s = .01 to .04) but these differences are not statistically significant. Using the reimprisonment recidivism measure, all the relationships between the type of prison and this recidivism measure are very slight (-.01 to +.01) and, again, not statistically significant.