The Bureau of Justice Statistics reports that a record 7.2 million Americans were incarcerated in 2006, costing taxpayers an estimated $45 billion and pushing states to consider less-costly alternatives ranging from private prisons to diversion to addiction treatment programs, the Washington Post reported June 12.

"There are a number of states that have talked about an early release of prisoners deemed non-threatening," said Rebecca Blank of the Brookings Institution. "The problem just keeps getting bigger and bigger. You're paying a lot of money here. You have to ask if some of these high mandatory-minimum sentences make sense."

The Pew Center on the States recently reported that the U.S. has more people in prison than any nation on earth, with 1 percent of the entire national population locked up. The new BJS report estimated that one in 15 black men are in prison, as well as one in 35 Hispanic males.

Harsh drug-crime sentencing laws have helped drive the prison population up from just 1.8 million in 1980. "It's really like a runaway train," said Ryan King of the Sentencing Project. "Nobody's taking a step back and asking where all these billions of dollars are going."

Still, the prison boom has its defenders. "If you look at the fact that these are people who are committing a crime, creating a danger to the public, you can't look at it as wrong," said Scott Thorpe, chief executive of the California District Attorneys Association. "What is the appropriate number of people to be incarcerated to ensure public safety? I don't know if you can answer that."

But Tim Lynch of the Cato Institute said the latest figures "demonstrate that we've lost our way ... when our laws require such a massive scale of incarceration."

"When you lock up a bank robber, a child molester or a mugger, you're removing a career offender from the street," said Lynch. "When you lock up a drug dealer, he is immediately replaced. We tried this with alcohol during Prohibition and it didn't work. We're not reaching the same conclusion with the drug war. It's slowly sinking in, but it will take politicians some time to turn this around."