Does Imprisonment Deter Crime?: James Q. Wilson sure thinks so

His piece in the LA Times is here:

Do we have too many people in prison?

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%. .. . .

Here was my take a few months ago.