The Deterrent Effects of Prison: Evidence from a Natural Experiment

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 postrelease 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