Relationship Between Prison Length of Stay and Recidivism: A Study Using Regression Discontinuity and Instrumental Variables With Multiple Break Points

Abstract

Research Summary In this study, we use both a regression discontinuity design and an instrumental variable identification strategy to examine the relationship between prison length of stay and recidivism among a large sample of federal offenders. We capitalize on the U.S. Sentencing Guidelines structure to apply these strong inference, quasi‐experimental approaches. We find that average length of stay can be reduced by 7.5 months with a small impact on recidivism. We also examine whether there is treatment heterogeneity. We find that length‐of‐stay effects do not vary by criminal history, offense seriousness, sex, race, and education level. Policy Implications We show that reducing the average length of stay for the federal prison population by 7.5 months could save the Bureau of Prisons 33,203 beds once the inmate population reaches steady state. This back‐of‐the‐envelope estimate reveals how reductions in time served can have a much larger impact on prison reductions compared with diverting low‐level offenders from prison to probation. Prison length‐of‐stay reductions can impact the entire prison population, whereas diversion typically affects a small subset of offenders whose consumption of prison beds is a small fraction of the total number of beds. We also discuss the potential impact of reducing levels of imprisonment on other collateral consequences.

Sentence Length and Recidivism

“…In contrast, Rhodes et al. () show that a modest across‐the‐board reduction in sentence length (of ∼7.5 months) could result in larger reductions in the federal prison population relative to the more popular targeted diversion strategies. The most important implication of a policy like this is that it would allow the Bureau of Prisons to close facilities.…”

“…Rhodes et al.’s () article offers an example leveraging more plausible comparisons and counterfactuals in pursuit of clear findings on the effects of incarceration for recidivism. The comparison offered here is across levels on a sentencing guidelines grid, where those just above or just below a particular cutoff are arguably similar with respect to propensity to recidivate but subject to different sentence lengths.…”

“…W illiam Rhodes, Gerald Gaes, Ryan Kling, and Christopher Cutler (2018, this issue) provide a compelling and rigorous analysis of the relationship between sentence length and recidivism. Exploiting federal sentencing guidelines and, importantly, the systematic disconnect between the guidelines and recidivism risk, Rhodes et al find that sentence length in the federal system could be reduced by 7.5 months with little impact on recidivism.…”

Anticipated Effects of Across‐the‐Board Reductions in Time Served

“…Rhodes et al. () provide strong quasi‐experimental evidence that the effect of sentence length on recidivism is small; they estimate that an increase of 7.5 months of incarceration is associated with a decrease in the 3‐year recidivism rate from 20% to 19%. They show that these results do not differ by sex, race, or education level.…”

“…Nevertheless, by adopting a conceptual model of criminology's influence undergirded with consistent production of high‐quality research such as that of Rhodes et al. (), a path may emerge that continues in the right direction.…”