When Are There Too Many People in Prison?
So the United States puts more people in prison than other countries? By itself that isnít evidence that something has gone wrong. Do higher arrest and conviction rates and longer prison terms, and the death penalty deter crime? The evidence that punishment deters criminals is overwhelming. While that evidence should be sufficient, the United States has a high prison population, but the United States also appears to have a relatively low violent crime rate compared to most other developed countries.
A sophisticated analysis wouldnít just say the penalties are too high, it would compare the costs of enforcement against the reduced costs from the crimes that are deterred. One good place to start is to recognize the benefits from deterrence. Changes in arrest rates account for up to about 18 percent of the variation in murder rates (see Lott, 2007, Chapter 4). Conviction rates explain up to another 12 percent. Prison sentences another 10 percent and the death penalty another 10 percent.
I donít put much weight in the cross-sectional analysis apparently favored by Loury simply because it is much easier to control for differences across countries with panel data, but the United Statesí high prison rate is at least balanced off by a relatively low violent crime rate. The International Crime Victimization Survey (ICVS) indicates that for the violent crime categories of sexual assault, robbery and aggravated assault, the U.S. looks remarkably safe.  This is even truer for the more serious categories of sexual assault and robbery. Prison is costly, but one could only imagine how much higher American crimes rates would be without it.
While murders make up only a fraction of violent crimes, they are by far the most costly type of crime. The ICVS doesnít compare murder rates. The U.S. white murder rate is comparable to many countries in Europe, and is just a fraction of Russiaís, one country that Loury compares the US to. The difference is driven blacks. Murders in the United States are overwhelmingly a minority problem. But the bottom line is that for murder deterrence matters. Even for the death penalty the vast majority of published refereed academic work finds that the death penalty deters crime (Lott, 2007, pp. 136-7).