This tool lets you try to end mass incarceration. But you’ll have to focus on violent offenders.

The US leads the world in incarceration, but most of its prisoners are in state prison. And a majority of state prisoners are serving sentences for violent crimes. That means that while states have made some progress in recent years in reducing their prison populations, it’s going to be extremely difficult for that trend to continue indefinitely.

This infographic, from the Marshall Project, shows how hard it is to reduce the prison population substantially just by targeting nonviolent, low-level offenders:

In September, Vox offered a few reasons why recent criminal-justice reforms haven’t made that much of a dent in the prison population. One reason is that they often targeted people who weren’t going to prison to begin with, rather than tackling the question of what to do with violent offenders.

The good news is that lawmakers don’t have to stop putting violent offenders in prison to reduce the incarceration rate substantially. They just have to stop putting them in prison for quite so long:

Experts say there should be reforms that let violent offenders, particularly those who are older and committed their crime decades ago, out early. The research indicates that people age out of crime, so letting them out of prison 10 or 20 years down the line might not pose a significant threat to public safety.

“While those people have committed serious crimes, in many respects their incarceration is often excessive,” says Marc Mauer, executive director of the Sentencing Project. “The person locked up on armed robbery at 19 is not necessarily the same person when he turns 30 or 40.”

To accomplish this, Mauer says state lawmakers would need to establish policies that make it so just about everyone — no matter what crime they were convicted of — can get parole or reduced sentences, through good behavior and evidence of rehabilitation. Policymakers could also take additional actions that relax or eliminate three-strike laws, mandatory minimum sentences, and other policies passed over the past three decades that force criminals to serve extremely long sentences.

This would present a dramatic shift in recent policy trends. According to the Sentencing Project, about one in nine US prisoners are currently serving a life sentence, and that rate has climbed over the past few decades. “Increasingly, those prison terms have overwhelmed any reductions we see on the lower levels of the scale,” Mauer says.