Chairman of AEI's Council of Academic Advisers James Q. Wilson

If you read a recent report by the Pew Center on the States, you would think so. As its title proclaimed, more than one in 100 American adults is in jail or prison. For young black males, the number is one in nine.

The report's authors contend that the incarceration rate represents a problem because the number of felons serving time does not have a "clear impact" on crime rates--and that all those inmates are costing taxpayers too much money to house. But nowhere in the report is there any discussion of the effect of prison on crime, and the argument about costs seems based on the false assumption that we are locking people up at high rates for the wrong reasons.

In the last 10 years, the effect of prison on crime rates has been studied by many scholars. The Pew report doesn't mention any of them. Among them is Steven Levitt, coauthor of "Freakonomics." He and others have shown that states that sent a higher fraction of convicts to prison had lower rates of crime, even after controlling for all of the other ways (poverty, urbanization and the proportion of young men in the population) that the states differed. A high risk of punishment reduces crime. Deterrence works.

But so does putting people in prison. The typical criminal commits from 12 to 16 crimes a year (not counting drug offenses). Locking him up spares society those crimes. Several scholars have separately estimated that the increase in the size of our prison population has driven down crime rates by 25%.

The Pew writers lament the fact that this country imprisons a higher fraction of its population than any other nation in the world, including Russia. But what they ignore is what the United States gets in return for its high rate of incarceration. For instance, in 1976, Britain had a lower robbery rate than did California. But then California got tough on crime as judges began handing out more prison sentences, and Britain became soft as laws were passed encouraging judges to avoid prison sentences. As a result, the size of the state's prison population went up while Britain's went down. By 1996, Britain's robbery rate was one-quarter higher than California's. Compared with those of the U.S. overall, Britain's burglary and assault rates are twice as high, according to a comparative study done by the U.S. Bureau of Justice Statistics.

These differences in crime rates involve many countries with low imprisonment rates. The robbery rate in the U.S. is not only lower than that in Britain but also that in Australia, Canada, the Netherlands, Poland, Portugal, Scotland and Spain, according to the same study. The imprisonment rate in these countries is one-fifth to one-tenth that in the United States.

You cannot make an argument about the cost of prisons without taking into account the benefit of prisons. The Pew report makes no effort to do this. Instead, it argues that spending on prisons may be crowding out spending on education. For instance, tax dollars spent on higher education in the U.S. have increased much more slowly than those spent on corrections. The report does not ask whether the slower growth may be in part because of the sharp increase in private support for public universities, much less whether society gets as much from universities as it does from prisons.

But Pew rightly points to problems in the nation's imprisonment policy and in what it does (or, typically, doesn't do) to prevent crime in the first place. Take California. It has failed to manage well the health--especially the mental health--problems of many of its inmates. Federal judges are in the process of imposing tough new rules to rectify the problem. Nor has the state found good ways to integrate former inmates back into society. Instead, parole officers routinely send people back to prison if they misbehave--and sometimes the return orders are for minor violations.

California does not handle drug offenders wisely either. Just how big this problem is remains uncertain because some inmates involved in serious crimes plead out to drug offenses to avoid tougher prison sentences. For serious drug users who have not committed a major crime, the goal should be to get them into a community treatment program and keep the offenders there.

To do that, we might emulate the HOPE (Hawaii's Opportunity for Probation with Enforcement) project in Honolulu. The program, started by state Judge Steven Alm in 2004, aims to get probationers to stay in a treatment program. Alm makes offenders take a random, mandatory drug test every week. If they fail, he immediately sends them to jail for a short time to discourage them from being on drugs. Within four years, according to a study by professors Mark Kleiman of UCLA and Angela Hawken of Pepperdine University, the violation rate among HOPE probationers fell by 90%. (Oddly, the Pew report, in discussing our "excessive" use of prison, makes no mention of the fact that there are about as many felons on probation as there are in prison.)

There is more that could be done to prevent young people from embarking on a life of crime. The Pew report rightly notes the success of the High/Scope Perry Preschool Project in Michigan, which began in the 1960s. The project has reduced delinquency among children of (mostly) poor black women by exposing them to a high-quality preschool program.

What we have learned from High/Scope is especially noteworthy because a random sample of youngsters were enrolled in the preschool program and the results were compared with those of a control group.

The Pew report could have mentioned at least 10 other crime-prevention programs that work. They can be found in "Blueprints for Violence Prevention," published by the Institute of Behavioral Science at the University of Colorado, and include Big Brothers/Big Sisters, nurse home-visitation programs and various special education programs in high schools. All were rigorously tested by controlled experiments in at least two locations.

But even with prevention programs, there will always be many people in prison. A major challenge for scholars today is to discover better ways of placing ex-inmates back into the community. If such methods can be devised, we can reduce the large number of parolees who are sent back to prison for violating the terms of their release.

But we should not suppose that, except for some minor drug offenders, we imprison too many people. There are still people who ought to be in prison and are not. There are more than 1 million felons on probation, in many cases because prisons are overcrowded, according to the Bureau of Justice Statistics. There are violent gang members who are hard to arrest and convict because their neighbors are afraid to go to the police or testify against them.

It is discouraging to read a report by an important private organization that can do no better than say we incarcerate too many people, get nothing from it and are stealing money from higher education.

James Q. Wilson is the chairman of AEI's Council of Academic Advisers.