If mass incarceration were an effective way to fight crime, then one would expect to see a strong correlation between higher rates of incarceration and reduced crime.

States have been running a live experiment of sorts on this over the past several years, reforming their criminal justice systems to, in short, punish people less punitively and incarcerate them for shorter periods of time for low-level offenses. Supporters of mass incarceration, such as the Trump administration and particularly Attorney General Jeff Sessions, have warned that these changes would lead to more crime.

But over the past few years, we’ve actually seen the opposite. Take this chart from Adam Gelb at Pew Charitable Trusts, which advocates for criminal justice reform, that shows crime has continued to fall even as states have reduced their prison populations:

Gelb pointed to one particularly telling statistic: “The average crime decline across the 10 states with the greatest declines in imprisonment was 19 percent, and across the 10 states with the largest imprisonment growth it was 11 percent.” In other words, the 10 states with the largest declines in imprisonment actually saw bigger drops in crime than the 10 states with the largest increases in imprisonment.

One caveat: There was an uptick in murder and violent crime rates in 2015 and 2016, based on some federal data. That led Sessions and other mass incarceration supporters to argue that criminal justice reforms had led to more crime. The good news, however, is that the data for 2017 so far indicates that violent crime and murder rates are once again on the decline, despite continuing reform efforts across the country.

The chart and these figures don’t by themselves prove that incarceration does nothing to combat crime. Studies, after all, find some connection. For example, a 2015 review of the research by the Brennan Center for Justice estimated that more incarceration — and its abilities to incapacitate or deter criminals — explained about 0 to 7 percent of the crime drop since the 1990s. Other researchers estimate it drove 10 to 25 percent of the crime drop since the ’90s.

But Pew’s chart and statistics are certainly not what advocates of mass incarceration would expect to see, indicating that the link between more incarceration and reduced crime is weak at best.

That’s particularly troubling because we know that incarceration has a lot of costs — not just in financial terms, but in its displacement of individuals and their communities too. For example, a 2015 New York Times analysis found that for every 100 black women out of prison, there are just 83 black men — what authors Justin Wolfers, David Leonhardt, and Kevin Quealy described as “1.5 million missing black men,” who could be fathers or workers in their communities but instead are behind bars.

Pew’s chart suggests that those costs are part of an ineffective scheme, and that it’s possible to undo incarceration without jeopardizing public safety.

For more on mass incarceration and its causes, read Vox’s explainer.