  This paper reviews the research on the impacts of incarceration on crime.
Where data availability permits, reviewed studies are replicated and
reanalyzed. Among three dozen studies I reviewed, I obtained or reconstructed
the data and code for eight. Replication and reanalysis revealed significant
methodological concerns in seven and led to major reinterpretations of four. I
estimate that, at typical policy margins in the United States today,
decarceration has zero net impact on crime outside of prison. That estimate is
uncertain, but at least as much evidence suggests that decarceration reduces
crime as increases it. The crux of the matter is that tougher sentences hardly
deter crime, and that while imprisoning people temporarily stops them from
committing crime outside prison walls, it also tends to increase their
criminality after release. As a result, "tough-on-crime" initiatives can reduce
crime in the short run but cause offsetting harm in the long run. A
cost-benefit analysis finds that even under a devil's advocate reading of this
evidence, in which incarceration does reduce crime in U.S., it is unlikely to
increase aggregate welfare.
