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Rick Scott, Governor
Florida Department of Corrections, Secretary Michael D. Crews

Florida Department of Corrections
Michael D. Crews, Secretary

Data and Methods: Release Cohort

Recidivism rates are calculated based on a release cohort—for this study, a group of prison inmates—released during a specified time period. The release cohort used to measure recidivism rates may vary. For example, a recidivism rate may be calculated for inmates released during a fiscal year or for all inmates released since a certain date. Because recidivism rates of state prison inmates do not vary much by year of release, this report relies on the latter method, calculating recidivism rates for inmates released from Department of Corrections custody from July 1995 through June 2001.

Data was collected on 106,167 prison releases involving 96,415 inmates during the six year study period. This number of releases is lower than those reported elsewhere by the Department, mainly because some inmates are released more than once on the same prison commitment. For example, an inmate who leaves prison on conditional release—a form of post-release supervision—can return to prison for a violation of supervision conditions (other than committing a new offense) and later leave prison again. For recidivism analysis, only the first such release is counted. Counting more than one of these releases would artificially lower the recidivism rates. This is because an inmate released twice who only recidivated after the second release would be counted both as a success (non-recidivist) and a failure.

Of these 106,167 releases, 2,643 (2.8%) were excluded from the analysis because they involved death, release out of state or to another prison system, escape, or a vacated (court-removed) sentence. Including these releases would also improperly lower the recidivism rates. Inmates released due to death cannot recidivate, and those released out of state are unlikely to recidivate in Florida. Releases to other prison systems must also be excluded because the true follow-up time can not be measured since the Department has no data on when the inmate was subsequently released. Those released by court-vacated sentences and the few who escape are excluded because they are unusual releases.

This analysis retained 85.7% of the 103,524 remaining releases (94,272 inmates), including 88,678 releases (81,737 inmates) with no missing data on important inmate characteristics relevant to recidivism. Almost all cases excluded for missing data have no score on the Test for Adult Basic Education because they did not take the test. Excluding these cases does not lower recidivism rate estimates in this study because the excluded cases have rates somewhat lower than those retained.

The study analyzed 80,919 releases of 74,467 male inmates and 7,759 releases of 7,270 female inmates. This study analyzes male and female releases separately, due to differences in their fundamental recidivism rates and because factors that influence recidivism affect males and females differently. Table 1 shows the final male and female cohorts broken down by the number of releases during each fiscal year (July - June) in the study period.

Table 1. Total Inmates
and Releases Analyzed
MALE FEMALE
N % N %
Inmates 74,467 91.1* 7,270 8.9*
Releases 80,919 91.3* 7,759 8.7*
Fiscal Year
Released
FY 1995-96 11,106 13.7 1,038 13.4
FY 1996-97 12,755 15.8 1,143 14.7
FY 1997-98 12,853 15.9 1,110 14.3
FY 1998-99 13,173 16.3 1,279 16.5
FY 1999-00 14,680 18.1 1,447 18.6
FY 2000-01 16,352 20.2 1,742 22.5
Note: * indicates the percentage of total cases analyzed.

For more information on recidivism rates based on fiscal year release cohorts, see Recidivism Rate Curves.

Table 2 describes the male and female release cohorts analyzed for this report. The characteristics presented are those found to predict recidivism rates best when used simultaneously. These characteristics were selected from 35 variables (counted in parentheses below) that cover 17 aspects of inmate characteristics in four general areas:

Demographic: gender (1), age (1), race (1), ethnicity (1)
Post release status: supervision (1), time not at risk (1)
Criminal History: onset / length (3), density (1), dispersion - geographic (1), diversity - offense specialization (2), severity offense volume, type, degree (11), prior supervision failure (2), prior recidivism (1)
Prison Experience: length of stay (1), behavior / confinement (5), custody level (1), education level (1).

Where possible, multiple ways of measuring each variable were tested. These measures are those that met three qualifications:

  • correlated most with recidivism among multiple measures for each variable,
  • correlated least with measures used for other variables, and
  • survived appropriately in tests of a variety of statistical models of recidivism.

This study only analyzed characteristics 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. Data is either unavailable or inadequate to analyze post-release factors such as employment, drug and alcohol use, and housing stability, etc., which may also affect recidivism rates according to other research.

For more information about how these cohort characteristics were measured and selected, see the Technical Appendix.

Table 2. Characteristics of Inmate Releases
FACTOR CATEGORY MALES FEMALES
N % N %
Gender 80,919 91.3* 7,759 8.7*
Age at Release UNDER 18 347 0.4 22 0.3
18 TO 24 20,046 24.8 930 12.0
25 TO 34 29,954 37.0 3,240 41.8
35 TO 49 27,334 33.8 3,336 43.0
50 TO 59 2,620 3.2 193 2.5
60+ 618 0.8 38 0.5
Mean / Std. Dev. 32.1 / 9.2 33.9 / 7.9
Max / Min 91 / 15 79 / 15
BLACK 47,343 58.5 4,449 57.3
HISPANIC 4,469 5.5 240 3.1
Supervision - Any After Release 29,982 37.1 1,998 25.8
Months in Prison 1-12 20,323 25.1 3,005 38.7
13-24 24,134 29.8 2,606 33.6
25-36 13,965 17.3 1,100 14.2
37-48 8,319 10.3 490 6.3
49-60 4,837 6.0 244 3.1
61+ 9,341 11.5 314 4.0
Mean / Std. Dev. 30.4 / 26.6 21.2 / 18.9
Max / Min 370 / 1 305 / 1
Disciplinary Reports - Total 0 36,396 45.0 4,302 55.4
1 13,491 16.7 1,294 16.7
2 7,218 8.9 586 7.6
3-6 12,059 14.9 861 11.1
7+ 11,755 14.5 716 9.2
Mean / Std. Dev. 3.2 / 6.9 2.3 / 6.4
Max / Min 208 / 0 113 / 0
Custody Level at Release COMMUNITY 2,650 3.3 337 4.3
MINIMUM 38,102 47.1 5,423 69.9
MEDIUM 26,719 33.0 1,705 22.0
CLOSE 13,448 16.6 294 3.8
Test for Adult Basic Education Grade Level - last before release 1-3.9 14,438 17.8 1,356 17.5
4-8.9 42,364 52.4 4,406 56.8
9-11.9 13,684 16.9 1,135 14.6
12-12.9 10,433 12.9 862 11.1
Mean / Std. Dev. 7.3 / 3.2 7.1 / 3.1
Max / Min 12.9 / 1 12.9 / 1
Prior Recidivism Events 0 41,631 51.4 4,606 59.4
1 17,291 21.4 1,599 20.6
2 10,459 12.9 856 11.0
3 6,228 7.7 444 5.7
4 3,176 3.9 171 2.2
5+ 2,134 2.6 83 1.1
Mean / Std. Dev. 1.0 / 1.4 0.7 / 1.1
Max / Min 11 / 0 7 / 0
Most Serious Offense Type- Career HOMICIDE 3,935 4.9 349 4.5
SEX/LEWDNESS 6,216 7.7 74 1.0
ROBBERY 17,227 21.3 906 11.7
OTHER VIOLENT 20,265 25.0 2,081 26.8
BURGLARY 17,322 21.4 882 11.4
PROPERTY 7,043 8.7 1,882 24.3
DRUGS 8,059 10.0 1,513 19.5
WEAPONS 338 0.4 17 0.2
OTHER 514 0.6 55 0.7
Property Offenses - Total 0 39,925 49.3 3,727 48.0
1 14,004 17.3 1,138 14.7
2 9,303 11.5 782 10.1
3+ 17,687 21.9 2,112 27.2
Mean / Std. Dev. 1.7 / 3.0 2.4 / 5.2
Max / Min 111 / 0 120 / 0
Drug Offenses - Total 0 41,163 50.9 3,103 40.0
1 11,686 14.4 1,085 14.0
2 8,822 10.9 954 12.3
3+ 19,248 23.8 2,617 33.7
Mean / Std. Dev. 1.6 / 2.5 2.2 / 2.9
Max / Min 35 / 0 41 / 0
Weapons Offenses - Total 0 69,543 85.9 7,304 94.1
1 7,879 9.7 359 4.6
2+ 3,497 4.3 96 1.2
Mean / Std. Dev. 0.2 / 0.6 0.1 / 0.3
Max / Min 8 / 0 4 / 0

These characteristics of the release cohorts are factors that influence recidivism rates: either raising or lowering an inmate's risk of recidivism. For information about these factors, see Statistical Analysis; and for how they affect recidivism rates, see Factors Affecting Rates.