Data Source: See the "Data sources" section of full report. (Graph: Elydah Joyce, 2022)

This graph originally appeared in Mass Incarceration: The Whole Pie 2022.

There are always at least two ways to look at the number of people incarcerated. Snapshots, like our annual Mass Incarceration: The Whole Pie report, provide the number of people in a correctional facility at a specific moment. At least as important is jail churn, which measures the number of times people are booked into a facility in a year.

Churn is especially important for local jails, where the population is constantly changing. Jails detain: (1) people who are not convicted of a crime (76%); (2) those who have been convicted and are generally serving misdemeanor sentences under a year; and (3) in most states, people held for federal or state law enforcement agencies. Some of the pretrial population will make bail within hours or days, but many will be detained until trial simply because they cannot afford to pay cash bail. The massive increase in pretrial detention has predominantly driven the tripling of the U.S. jail population since the 1980s. Among people in local jails who have been convicted, three-quarters are serving sentences for nonviolent offenses.

Because of the different moments at which people make bail and the shorter sentences, while 600,000 people enter prison gates every year, people go to jail 10.6 million times each year. While churn does not measure the number of unique individuals that are booked into jail annually, we recently filled this data gap. At least 4.9 million people are arrested and jailed each year, and at least one in 4 of those individuals are booked into jail more than once during the same year.