Crime has fallen dramatically in recent decades. The number of people in jail for committing crimes hasn’t.

New Bureau of Justice Statistics data reveal that jails held 745,200 inmates in 2017, virtually identical to the 747,500 they held in 2005, and significantly higher than the 584,400 they held in 1998. How does the correctional system keep jails full when there just aren’t as many crimes as there used to be? By locking up an increasing number of people who are awaiting trial and could well be innocent.

The number of individuals held in jail while awaiting trial has soared 45.3 percent, from 331,800 in 1998 to 482,000 in 2017. By contrast, the number of convicted inmates is almost the same as it was 20 years ago (252,600 in 1998 vs. 263,200 in 2017). About 95 percent of the jail population’s growth is thus accounted for by people who haven’t been convicted of a crime.

By jailing more and more people who are awaiting trial, the criminal justice system can keep jails full no matter how much crime falls. This may be seen as a good thing by the hundreds of thousands of people who work in jails, the companies that supply services to jails (i.e., food), and the communities that value correctional facilities as a form of economic stimulus. But it’s a world-class bug from the point of view of innocent people who are jailed while awaiting trial, not to mention taxpayers.

Given the internal incentives to keep jails full, change will have to come from outside the criminal justice system. The most obvious lever available, which is picking up steam in multiple states, is bail reform. States could simply mandate that individuals accused of low-level crimes are automatically released on their own recognizance before trial. Jurisdictions that have experimented with this approach have found rates of appearing at trial in excess of 98 percent.

States could also mandate that when bail is deemed appropriate, the cash amounts required be reduced so that more accused individuals could pay rather than be jailed until trial. Human beings have at least some loss-aversion that doesn’t correlate with the size of the loss. In other words, the prospect of forfeiting $250 bail for not appearing at trial could be almost as motivating as the prospect of forfeiting $1,000. Cutting the monetary amounts specified in bail schedules would upset bail bondsmen but would probably benefit the public.

States, cities and counties should also consider closing or at least downsizing jails. If the system is going to find ways to keep every bed full regardless of the crime rate, cutting the number of beds available may be the only way to prevent an increasing number of people accused of crimes from being punished as harshly as those who are actually convicted.