Incarceration has meaningful reoffending-reducing average effects that diminish in incarceration length; as a result, budget-neutral reductions in sentence length combined with increases in incarceration rates can decrease recidivism

How Does Incarceration Affect Reoffending? Estimating the Dose-Response Function. Evan K. Rose and Yotam Shem-Tov. Journal of Political Economy, Jul 2021. https://www.journals.uchicago.edu/doi/abs/10.1086/716561

Abstract: We study the causal effect of incarceration on reoffending using discontinuities in North Carolina’s sentencing guidelines. A regression discontinuity analysis shows that one year of incarceration causes a reduction in the likelihood of being reincarcerated within three, five, and eight years from sentencing by 44%, 29%, and 21%. To parse the potentially heterogeneous dose-response relationship underlying these effects, we develop an econometric model of prison sentences and recidivism. We find that incarceration has meaningful reoffending-reducing average effects that diminish in incarceration length. As a result, budget-neutral reductions in sentence length combined with increases in incarceration rates can decrease recidivism.

6 Concluding remarks

Our analysis shows that incarceration substantially reduces reoffending in the years after sentencing. The effects are not concentrated among a specific type of criminal incident: we observe reductions in violent, property, and drug crimes, as well as reincarceration overall. We then use a Roy-style selection model to parse the heterogeneous dose-response underlying these effects. We find that the average treatment effects of incarceration are diminishing in sentence length. In addition, we find that while the offenders given longest sentences have the highest recidivism risk, they also experience the largest reductions in reoffending due to exposure to prison. Budget neutral changes in sentencing that take advantage of these patterns by shortening sentences overall but sending a larger fraction of offenders to prison can generate meaningful reductions in recidivism. This exercise, however, speaks only to better allocations of sentences given current levels incarceration spending; it does not imply that all offenders should be incarcerated for at least a brief period. Indeed, a broader cost-benefit analysis may find it is optimal to reduce incarceration overall. Our estimates are an important contribution to the on-going debate over U.S. criminal justice policy. After growing steadily since the 1970s, incarceration rates began to decline slightly in the mid-2000s. Recent policy changes, however, have the potential to at least check these recent reductions. While our estimates show that incarceration sentences do not increase reoffending, they also demonstrate that incarceration has room to rehabilitate inmates further, especially when compared to carceral regimes in other developed countries such as Norway. Since incarceration is unlikely to be abolished in the near future, understanding what features of imprisonment itself can be rehabilitative or damaging to offenders is a useful area for future research