Incarceration rates and crime: A counter-intuitive relationship

The lock-em-up logic of mass incarceration holds that prison expansion keeps more criminals off the street and therefore reduces crime. But that's an hypothesis, not a fact. Luckily, differing incarceration policies among states in recent years have supplied a natural experiment to test the theory, which turns out to be full of holes. In fact, a new analysis from Pew analyzing the state-by-state data found that jurisdictions which reduced incarceration most saw higher drops in crime rates.

Crime has declined across the western world and throughout the United States since the 1990s, but at the state level there have been variations. From 2010 to 2015, according to Pew, 35 states saw reductions in incarceration rates while 44 states saw reductions in violent and property crime.

Digging more deeply, the states which reduced incarceration most saw higher crime reductions. "In the 10 states with the largest imprisonment declines, the crime rate fell an average of 14.4 percent, compared with 8.1 percent in the 10 states with the biggest growth in imprisonment."

Of the 10 states with the largest imprisonment reduction, Texas' rate remained by far the highest. Still, Texas' imprisonment rate declined 12.9 percent from 2010 to 2015, emblemized by the closure of three prison units, while our crime rate declined 23.3 percent.

Pew offered this understated conclusion: "The lack of a consistent relationship between the crime and imprisonment trends reinforces the findings of the National Research Council and others that the imprisonment rate in many states and the nation as a whole has long since passed the point of diminishing public safety returns." Grits would put the lesson from their research more plainly: The evidence shows incarcerating fewer people does not correlate with increased crime and in fact, correlates more strongly with larger crime reductions.