Why Has Crime Declined in the U.S.?

Editor’s Note: This article previously appeared in a different format as part of The Atlantic’s Notes section, retired in 2021.

We’ve had a flood of thoughtful, nuanced questions in response to our call-out about mass incarceration. We asked what our readers wanted to know in the wake of Ta-Nehisi Coates’s cover story—what lingering questions they had and what else about the topic they were curious about.

One question in particular leapt out among the responses: Why did the U.S. see crime rates rise, and then fall, over the past two generations?

This question is one of the larger mysteries of crime in the U.S. at the moment, although a lot of recent attention centers on the surge reported in several large cities this summer. (So far this is one deviation in a broader fall. Gene Demby of NPR’s Code Switch pointed this out on Twitter, yielding a handy chart that laid out Washington, D.C.’s homicide rate decline since 1990.)

Earlier this year, Inimai Chettiar wrote for The Atlantic about the fall in crime as it relates to the rise in incarceration over the last two decades. A causal relationship would seem to make sense—locking up more people should mean there are fewer baddies on the street to commit crime, right? But researchers from the Brennan Center for Justice at the NYU School of Law found that the growth in incarceration played a bit part in falling crime rates.

Even with all the known factors involved in declining crime, including higher incarceration rates, we still can’t account for the full cause. Take a look at these graphics exploring popular theories of the drop between 1990-99 and 2000-13:

Brennan Center

That massive piece of the pie in a medium shade of grey comprises the unknown factors at play. Not a terribly satisfying answer, but that’s the data we’ve got.

Inimai Chettiar put it like this:

No one factor brought down crime. Today, incarceration has become the default option in the fight against crime. But more incarceration is not a silver bullet. It has, in fact, ceased to be effective in reducing crime—and the country is slowly awakening to that reality. Incarceration can be reduced while crime continues to decline. The research shows this and many states are watching it unfold.

We’re continuing to look into mass incarceration and its effects. What else would you like to know about the subject?