Jailing People Has Little Effect on Crime Levels

At some point, the data indicates, more people in prison doesn’t translate to fewer crimes


The U.S. incarceration rate is extreme—the highest in the world since 2002, even after modest declines in 2014. Is that expense worth it? To explore this issue, the New York University School of Law’s Brennan Center for Justice produced a report, published this week, that delves into data on crime and incarceration rates across the country. What they found suggests that more people in prison doesn’t necessarily translate to fewer crimes.

At FiveThirtyEight, one of the authors, Oliver Roeder, hits the report’s highlights.

The data do not argue against incarceration. But they do suggest that there’s a point beyond which imprisoning more people just isn’t worth it. Roeder writes at FiveThirtyEight:

Once the worst offenders are in prison, each additional prisoner will yield less benefit in the form of reduced crime. Increased incarceration — and its incapacitation effect — loses its bite. And at its world-historic level, it’s not surprising that it would’ve lost nearly all of it.

But the data truly backing that assertion are lacking, at least at the broad scale. So the report instead dives into some different between states in the U.S. that provide "anecdotal evidence of diminishing incarceration returns." Roeder again:

For example, California had to decrease their incarceration rates to address overcrowding in their prisons — a change mandated by the Supreme Court. However, from 2000 to 2013 the state actually saw a significant decrease in violent crime rate. Thirteen other states, including New York and Texas, also saw decrease in violent crime at the same time as their decrease in incarceration. Only two states that made an effort to put fewer people in prison faced increases in violent crime.

The best suggestion to actively reduce crime isn’t to increase incarceration, the report suggests, but to get better at policing. To back this up, the authors offer evidence that use of a computerized system called CompStat to keep track of crime data in several major cities has coincided with drops in crime rates.

All the evidence lines up with other arguments against  the high U.S. incarceration rate. For example, when people are given longer sentences for their crimes, their peers are more likely to end up in prison — incarceration is contagious. At the very least, the report adds to mounting evidence that if rehabilitation and a safer, more lawful society is the goal, then strategies other than mass incarceration are worth considering.

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