Like Rhode Island, states across the country are fighting decades of explosive growth in their prison populations.
Fueled by stiffer sentencing and release laws, prison populations rose precipitously starting in the early 1970s. The war on drugs and zero-tolerance laws on crime sent the prison population soaring in the 1980s and '90s.
Between 1925 (the first year national prison statistics were collected) and 1972, the prison population increased by 105 percent.
In the nearly four decades since then, the prison population grew by 705 percent, according to the Bureau of Justice Statistics. Today, about 1 in 100 adults in the US lives behind bars. The Pew report findings mark the first dip in the state prison population since 1972.
"Is this a tap of the brakes or a shift into reverse?" asks Mr. Gelb, of the Pew Center. "It's too soon to tell, but we think there's several reasons [behind the drop]."
At the top of the list is money.
Over the past two decades, corrections spending has jumped from $11 billion to more than $50 billion. It's the second-fastest-growing state budget category behind Medicaid.
"There's not a warden [who] wouldn't tell you that these costs … are bankrupting them," says Ted Kirkpatrick, codirector of Justiceworks, a crime and justice research group at the University of New Hampshire in Durham.
Some states, such as California, plan to release inmates before their sentences are complete.