Nearly 2.2 million Americans now live behind bars, about eight times as many as in 1975 and the most per capita in the Western world. For three decades, Congress and dozens of legislatures have worked to write tougher anti-crime measures. Often the only controversy has centered on how to finance the construction of prison cells.

In New York, officials are shutting down prison cells. Elsewhere, it's a different story.

Perhaps as intriguing is the experience in states where officials spent billions of dollars to build prisons. From 1992 to 2002, Idaho's prison population grew by 174 percent. the largest percentage increase in the nation. Yet violent crime in that state rose by 14 percent. In West Virginia, the prison population increased by 171 percent, and violent crime rose 10 percent. In Texas, the prison population jumped by 168 percent, and crime dropped by 11 percent.

Other states are now beginning to re-think their overreliance on prisons:

In the past few years, legislators in such conservative states as Louisiana and Mississippi have passed sentencing reforms. Kansas and Nebraska are reconsidering prison expansion in favor of far less expensive drug treatment. The United States annually spends about $60 billion on prisons.

If you don't care because you don't know anyone in prison, you should. This affects you too.

"Crime is down and people realize, sure, we can lock up more people, but that's why your kid's pre-K class has 35 kids -- all the money is going to prisons," Jacobson says. "There's a sense of urgency that for the first time in two decades, we can talk about whether it makes sense to lock up even more people."

The pro- lock 'em up crowd thinks more people in prison reduces crime since fewer criminal are out there able to commit offenses. But, others point out:

The nation's prison population rose between 1985 and 1993 -- even as crime spiked sharply. New York was not the only city in which crime and imprisonment fell in tandem during the 1990s. From 1993 to 2001, homicides in San Diego declined by 62 percent while prison sentences dropped by 25 percent.

Casting an eye north of the border, Canada experienced a sharp drop in crime as its prison population fell.

Who's in jail these days?

Approximately 60 percent of U.S. convicts serve time for charges related to drug peddling and addiction. In California, 65,000 parolees fail drug tests each year and are recycled back to prison each year. They serve, on average, an additional four months, at a cost of $1 billion.

Then there's the social cost of incarceration:

Such heavy reliance on prison, epidemiologists note, carries a considerable social price tag. Hundreds of thousands of released felons cannot vote, cannot obtain driver's licenses and have trouble finding jobs -- a toll that falls disproportionately on blacks, Latinos and poor whites.

Don't give credit for lowering the jail population to Rudy Giuliani either:

No public official set out to drive down New York's prison and jail population in the early 1990s. Quite the opposite; crack-fueled homicides had topped 2,000, the middle class was fleeing and Giuliani was elected on a crime-fighting platform.

"If I told Rudy we needed to lock up 40,000, 50,000 people, he would have said fine," Jacobson said. "Rudy can say now that he's a genius, but the drop in prison population was entirely unintentional."

As for why crime may be lower in New York, consider this:

City and state prisons in New York also turned aggressively to drug treatment and mental health counseling. They did so as a matter of enlightened self-interest. The city prison system is the second-largest mental health provider in the nation; only the Los Angeles County system surpasses it.

Rehabilitation. Try it, it works.