For the first time since President Richard Nixon won reelection in 1972, the number of people behind bars in state prisons declined last year, according to a new survey, Prison Count 2010, conducted by the Pew Center on the States. As of January 1, there were 1,403,091 people doing state prison time, a decline of 5,739, or 0.4%, from December 31, 2008.

The state prison population has increased seven-fold since 1972, driven by harsher sentencing laws, including drug laws, and an ever larger number of people under correctional supervision, who are eligible to be sent to or back to prison for violating the conditions of their probation or parole. People sentenced for drug offenses typically account for somewhere between 20% and 25% of state prison populations.

The drop was driven was by significant declines in prison populations in states like California, Maryland, Michigan, Mississippi, New York, and Texas, where sentencing and parole reforms passed in recent years are beginning to take hold. California saw the largest decline in absolute numbers, shedding 4,257 prisoners last year, followed by Michigan (down 3,260), New York (down 1,699), Maryland (down 1,315), Texas (down 1,257), and Mississippi (down 1,233).

But there was also wide variation among the states. Twenty-seven states saw declines, while 23 saw increases, some significant. In the 23 states where the state prison population grew, more than half of the increase occurred in just five states: Pennsylvania (2,122), Florida (1,527), Indiana (1,496), Louisiana (1,399) and Alabama (1,053).

"After so many years on the rise, any size drop is notable. What's really striking is the tremendous variation among the states," said Adam Gelb, director of the Pew Center on the States' Public Safety Performance Project."These numbers highlight just how much the decisions by state policymakers impact the size and cost of prison systems."

States have gotten smarter -- as opposed to tougher -- on crime, Gelb said. "The decline is happening for several reasons, but an important contributor is that states began to realize there are research-based ways they can cut their prison populations while continuing to protect public safety," he said. "In the past few years, several states have enacted reforms designed to get taxpayers a better return on their public safety dollars."

The trend pre-dated the economic recession, he noted. "These types of policy changes are not simply a response to the economic downturn," said Gelb. "Before this recession began, states like Texas recognized that by strengthening their probation and reentry programs they could cut corrections spending, protect public safety and hold offenders accountable for their actions."

It's a different story with the federal prison population, the report found. The number of federal prisoners continued to grow, increasing by 3.4% in 2009 to an all-time record 208,118. More than 60% of federal prisons are doing time for drug offenses.

The increase in federal prisoners was enough to outweigh the decrease among state prisoners, and the combined state and federal prison population grew by 1,099 last year.

The state and federal prison numbers do not include jail inmates. When they are added in, said Pew, the nation's incarceration rate remains unchanged, with some 2.3 million people behind bars.