One of the goals of imprisonment is to reduce violence¹. Although imprisonment has risen dramatically since the 1970s, its effects on future violent crime are poorly understood². This study's objective was to examine the effect of imprisonment on violent crime in the community among individuals on the policy margin between prison and probation sentences. Drawing on data from a population-based cohort of individuals convicted of a felony in Michigan between 2003 and 2006 (n = 111,110) and followed through June 2015, we compared the rates of commission of violent crime committed by individuals sentenced to prison with those of individuals sentenced to probation using a natural experiment based on the random assignment of judges to criminal cases. Being sentenced to prison had no significant effects on arrests or convictions for violent crimes after release from prison, but imprisonment modestly reduced the probability of violence if comparisons included the effects of incapacitation during imprisonment. These results suggest that for individuals on the current policy margin between prison and probation, imprisonment is an ineffective long-term intervention for violence prevention, as it has, on balance, no rehabilitative or deterrent effects after release.

Because of racially disproportionate imprisonment rates, the literature on mass incarceration has focused on the labor market consequence of imprisonment and the implications of those effects for racial inequality. Yet, the effects of imprisonment itself, as distinct from conviction, are not well understood. The authors leverage a natural experiment based on the random assignment of judges to felony cases in Michigan to examine the causal effect of being sentenced to prison as compared to probation, stratifying by race and work history. The most widespread effect of imprisonment on employment occurs through incapacitation in prison, both for the initial prison sentence and through the heightened risk of subsequent imprisonment. Negative postrelease effects of imprisonment on employment, employment stability, and employment outside the secondary labor market are concentrated among whites with a presentence work history. Postrelease effects of imprisonment on employment among those with no work history are positive but fade over time.

A substantial contributor to prison admissions is the return of individuals recently released from prison, which has come to be known as prison's "revolving door." However, it is unclear whether being sentenced to prison itself has a causal effect on the probability of a subsequent return to prison or on criminal behavior. To examine the causal effect of being sentenced to prison on subsequent offending and reimprisonment, we leverage a natural experiment using the random assignment of judges with different propensities for sentencing offenders to prison. Drawing on data on all individuals sentenced for a felony in Michigan between 2003 and 2006, we compare individuals sentenced to prison to those sentenced to probation, taking into account sentence lengths and stratifying our analysis by race. Results show that being sentenced to prison rather than probation increases the probability of imprisonment in the first 3 years after release from prison by 18 percentage points among nonwhites and 19 percentage points among whites. Further results show that such effects are driven primarily by imprisonment for technical violations of community supervision rather than new felony convictions. This suggests that more stringent postprison parole supervision (relative to probation supervision) increases imprisonment through the detection and punishment of low-level offending or violation behavior. Such behavior would not otherwise result in imprisonment for someone who had not already been to prison or who was not on parole. These results demonstrate that the revolving door of prison is in part an effect of the nature of postprison supervision.