One person is sentenced to state or federal prison every 90 seconds in the United States, amounting to almost 420,000 per year. The U.S. has the highest incarceration rate in the world. But how much safety does all this imprisonment actually buy us? A study I recently published with colleagues shows the answer is very little, especially in the long-term. The study found that sentencing someone to prison had no effect on their chances of being convicted of a violent crime within five years of being released from prison. This means that prison has no preventative effect on violence in the long term among people who might have been sentenced to probation. It also found a preventative ... effect in the short term, during the time when prisoners were still in prison, but this effect is smaller than we typically assume. Preventing one person who was previously convicted of a violent crime from committing a new violent crime within five years of their sentence requires imprisoning 16 such individuals. The short-term and small preventative effect of prison means those dollars could be better spent on other violence prevention or public safety strategies. The high costs of prison combined with concerns about the negative collateral consequences for prisoners, their families, and communities have prompted renewed efforts ... to reduce imprisonment. Yet despite the fact that over half of prison inmates were convicted of a violent crime, most criminal justice reforms exclude those with violent pasts.