“The Deterrent Effects of Prison: Evidence from a Natural Experiment”, 2009-04 (; backlinks):
The Collective Clemency Bill passed by the Italian Parliament in July 2006 represents a natural experiment to analyze the behavioral response of individuals to an exogenous manipulation of prison sentences.
On the basis of a unique data set on the post-release behavior of former inmates, we find that:
1 month less time served in prison commuted into 1 month more in expected sentence for future crimes reduces the probability of recidivism by 0.16 percentage points.
From this result we estimate an elasticity of average recidivism with respect to the expected punishment equal to −0.74 for a 7-month period.
…A. Data: The source of data for this study is an internal database that the Italian DAP maintains on offenders under its care. We were granted access to the DAP database records on all the individuals released as a result of the collective pardon law between August 1, 2006, and February 28, 2007. The full sample includes 25,813 individuals; 81% were released on August 1, 2006. For each individual, the data provide information on whether or not he or she reoffends within the period between release from prison and February 28, 2007. This means that for most of the individuals the data report recidivism in the first 7 months after release from prison. Moreover, the data set contains information concerning a large set of variables at the individual and facility levels. For each individual, information is reported on the facility where the sentence was served, the official length of the sentence, the actual time served in the facility, the kind of crime committed (ie. the last crime committed in the individual’s criminal history), age, sex, level of education, marital status, nationality, province of residence, employment status before being sentenced to prison, and whether the individual had a final sentence or was waiting for the first verdict or for the result of an appeal at the date of release. As data on subsequent convictions are not available, we use a subsequent criminal charge and imprisonment as the measure for recidivism.