Sending crooks to prison reduces crime

Charles Murray:

I got into a good-natured argument with my friend Pete Wehner of the Ethics and Public Policy Center over lunch last week about the importance of incarceration in explaining the gratifying drop in crime since the 1990s. Pete cited some credible technical analyses (summarized in John DiIulio’s fine overview on crime trends showing that increased incarceration accounts for only 10 to 35 percent of the reduction in crime), while I muttered that we would see how true that is if we freed a whole lot of violent criminals. Without pretending to refute the technical analyses, let me give a quick illustration why I think simple incapacitation—we’ve locked up a huge percentage of the really nasty guys—plus a substantial deterrent effect is a plausible explanation for why violent crime dropped at all.

I specify violent because I’m sure that much of the drop in property crime is explained by target hardening. It’s impossible to steal most new cars this day because there is no way to get the engine started without the key. Hot-wiring is futile. Try to burgle a home in a neighborhood where homes have much worth stealing, and you’d better be prepared to get in and out before the high-tech security system brings the cops. If you’re in a commercial area, you’ve got omnipresent surveillance cameras to worry about along with the security systems. The effect of these innovations on violent crime has been much spottier. Yes, it can be harder to rob a convenience store (robbery is classified as a violent crime), but for the most part, robbery, homicide, aggravated assault, and rape are not technically more difficult to commit than they used to be.

Here is a graph that shows the violent crime rate per 100,000 population and the number of prisoners per 1,000 violent offenses from 1960–2010:

Source: Bureau of Justice Statistics, FBI Uniform Crime Reports. “Prisoners” refers to inmates of state and federal prisons and does not include persons in jail.

... 

The graph is very telling.  It is a warning to those who think we should reduce the prion population to save money.  Liberals still seemed amazed by the fact that a high prison population reduces crime.  It is hard to argue with the graphic though.