Measuring the Incapacitation Effect of Incarceration

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A central question in the fields of criminology and the economics of crime concerns the extent to which incarcerating the criminally active reduces national crime rates. The short-run causal pathways connecting incarceration to crime are two-fold. First, those who are incarcerated cannot commit crimes. Second, individuals may be deterred by the threat of incarceration. Despite the simplicity of these ideas, the results from empirical research vary considerably. Much of this research suffers from a key problem: any societal forces that increase criminal activity will increase the incarceration rate. For example, if the economy were to sour and more people commit crime as a result, more people will be arrested and sent to prison. In the aggregate, we observe crime increasing as incarceration increases, creating the false impressions that incarceration increases crime.This project will measure the effect of incarceration on crime by making use of an unusual policy event. In August 2006, the Italian government released one-third of the nation's prison inmates in an effort to relieve prison overcrowding. Any inmate with less than three years remaining was immediately released. As a result, in August of 2006 the Italian prison population declined abruptly, discretely, and substantially. Since this change in incarceration was clearly driven by a policy choice rather than changes in external factors that cause crime, any observable changes in crime surrounding the pardon can be attributed to the change in the prison population. This project will evaluate the impact of this pardon on Italian crime rates. The resulting empirical results will provide estimates of the amount of crime caused by prisoner releases and will be used to produce estimates of the annual crimes prevented through incarceration. Most importantly, the project will provide estimates that are free from bias associated with a reverse impact of crime on incarceration.