A new report from the U.S. Department of Justice suggests that after more than 30 years of increases, the prison population has leveled off and in fact has started to decline.

"There were 6.98 million offenders under the supervision of the adult correctional systems at yearend 2011, a decrease of more than 98,900 offenders during the year," the report says.

The report indicates that the cause of the declining prison population is not a decrease in crime but rather related to changing policies about how long to hold prisoners. Department of Justice researchers note that while the number of people sentenced to prison in 2011 increased by 3.4 percent, more people were release from prison.

Money seems to be a cause of the declining prison population. "More people are being released from prison recently because one way states are saving money in grim budgetary times is by expanding parole programs and early releases," reported the New York Times.

The turnaround in incarceration rates has been under-reported in the media, according to Stanford University professor of psychiatry Keith Humphreys, because "officials who have helped reduce incarceration are scared to publicly take credit for it," he wrote in a post for his blog Reality Based Community.

"At least a handful of the roughly 100,000 fewer people under correctional supervision in 2011 versus 2010 for example will do something extremely violent and high-profile," according to Humphreys, "and no politician wants to risk being in a story headlined 'Convict released by thug-loving governor murders nun.’ ”

"Prisons in California and other states like Louisiana are beginning to institute 'medical parole' initiatives designed to save costs by releasing some older prisoners early," according to a radio program by Southern California Public Radio (SCPR).

Advocates of this type of initiative "say that older prisoners do not pose a threat to society," said SCPR, and releasing them would greatly reduce costs. However, SPCR spoke with other experts who suggest that the savings won't be that great because the "cost liability may just be switched to programs like Medicare, which pays at least some medical costs for the elderly."