Analyzing the Impact of Postprison Supervision on Rearrest Outcomes
By Amy L. Solomon, Vera Kachnowski, Avi Bhati, Urban Institute

In this research brief, we use data from a Bureau of Justice Statistics (BJS) recidivism study  to compare prisoners released to parole supervision in 1994 with prisoners who completed their entire prison sentence and were released without any supervision or reporting requirements. The goal is to assess, at an aggregate level, whether parole "works" at reducing recidivism among those who are supervised after release from state prison.
The report is organized around three key questions. First, do prisoners released with and without supervision differ with respect to demographics, incarceration characteristics, and criminal histories? Second, do prisoners released with and without supervision recidivate at different rates? And finally, if there are differences in recidivism outcomes between those released with and without supervision, when and for whom does supervision matter most?

http://www.urban.org/UploadedPDF/311156_Does_Parole_Work.pdf