DALLAS - The United States prison population may soon drop for the first time in almost four decades, a milestone in a nation that locks up more people than any other.

The inmate population has risen steadily since the early 1970s as states adopted get-tough policies that sent more people to prison and kept them there longer. But tight budgets now have states rethinking those policies and their costs.

"It's a reversal of a trend that's been going on for more than a generation," said David Greenberg, a sociology professor at New York University. "In some ways, it's overdue."

The U.S. prison population dropped steadily during most of the 1960s, and there were a few small dips in 1970 and 1972. But it has risen every year since, according to the Bureau of Justice Statistics.

Approximately 739,000 prisoners were admitted to state and federal facilities last year, about 3,500 more than were released, according to new figures from the bureau. The 0.8 percent growth in the prison population is the smallest annual increase this decade and significantly less than the 6.5 percent average annual growth of the 1990s.

Overall, there were 1.6 million prisoners in state and federal prisons at the end of 2008.

Historically, prison populations have been lower when military drafts were enacted, including during World War II and the wars in Korea and Vietnam.

"People who go to war are young men, and young men are the most likely to get arrested or prosecuted," said James Austin, president of the JFA Institute, a research organization that advises states on prison matters.

The wars in Iraq and Afghanistan have not involved a draft.

Instead, the economic crisis forced states to reconsider who they put behind bars and how long they kept them there, said Kim English, research director for the Colorado Division of Criminal Justice.

States also are looking at ways to keep people from ever going to prison. A nationwide system of drug courts takes first-time felony offenders caught with less than a gram of illegal drugs and sets up a monitoring team to help with case management and therapy.

"I don't think they work. I know so," Judge John Creuzot in Dallas said.