Skip to main content
U.S. flag

An official website of the United States government

Conducting Randomized Controlled Trials in State Prisons (2020)

State prisons nationwide house approximately 1,306,000 inmates, which is more than half (57%) of the total population of incarcerated individuals on any given day in the United States. The incarceration rate for those in state prisons increased from 87 sentenced inmates per 100,000 residents in 1970 to a peak of 447 sentenced inmates per 100,000 residents in 2008, more than a 400% increase. Since 2008, the state prison incarceration rate has decreased slightly, to 390 sentenced inmates per 100,000 residents. Approximately 562,000 inmates are admitted to state prisons each year, of which about two-thirds are sentenced by the court and one-third are community supervision violators. Approximately 573,000 inmates are released from state prisons each year, of which nearly 80% are conditionally released to community supervision and the remaining 20% are unconditionally released. The average sentence length for those sentenced to state prisons is 6.4 years, and the average actual length of stay in prison is 2.6 years. Just over half of state prison inmates (55%) were originally committed for a violent offense, 18% for a property offense, 15% for a drug offense, 11% for a public order offense (e.g., weapons), and 1% for some other type of crime.5 According to a recent national estimate, about 83% of inmates released from state prisons are rearrested within nine years of release.

Notice about external resources

These links are being provided as a convenience and for informational purposes only; they do not constitute an endorsement or an approval by the National Institute of Corrections (NIC) of any of the products, services or opinions of the corporation or organization or individual. NIC bears no responsibility for the accuracy, legality or content of the external site or for that of subsequent links. Contact the external site for answers to questions regarding its content.