Last year, the United States prison population fell to its lowest rate since 1997, according to new statistics released by the Department of Justice this week.  The total number of federal and state inmates at the end of 2015 dropped by 2.3 percent from the previous year, the largest drop since 1978. There were 458 inmates per 100,000 US residents last year, the lowest number since 1997, when there were 444 inmates per 100,000 Americans.

The Department of Justice claims that the decrease in prison population is thanks to changes in both federal and state corrections policies, including drug treatment and drug decriminalization efforts. Federal prisons accounted for 40 percent of the decline, as the number of federal inmates fell to 196,500. One of the reasons for the larger drop in the federal incarcertation rate was the release of 6,000 nonviolent drug offenders as part of President Obama's commitment to prison reform. The President also shortened the sentences of 1,176 other federal inmates this year.

The population of state prisons also declined by around 2 percent, as 29 states reported a decrease in the number of prisoners. The prison population has slowly fallen by 6 percent after reaching a peak in 2009, but the US incarceration rate is still the highest in the world. Roughly 1 out of every 37 Americans was behind bars at the end of 2015. When taking people out on parole or probation into account, there were a total of 6.74 million people under the supervision of state and federal correctional systems at the end of 2015.