During the 1980s violent crime rose to new peaks. The murder rate in 1991 reached 9.8/100,000, about four times the rate in, say, France. A criminologist named George Kelling argued that the toleration of all sorts of little crimes or acts of indecency—even broken windows or vandalism or those homeless goofs at intersections trying to extort pocket change for cleaning your windows—created an atmosphere of disrespect for the law. From little things, people went on to feel less restrained about bigger things. Kelling sold this idea to New York City Police Commissioner William Bratton. New York cops started pushing the homeless into shelters, clearing the intersections of squeegee men, and stopping kids from hanging out on street corners.

However, Bratton also embraced the idea that a lot of crime is committed by a few people, and a little crime is committed by a lot of people. You want a big drop in crime? Concentrate on the few career criminals and put them away for a long time. Bratton concentrated on a statistical analysis of crime in each police precinct, then drove his precinct captains to find and arrest habitual criminals. This seemed to work, so lots of police departments adopted the New York approach. Bratton’s approach coincided with a get-tough policy adopted by legislatures in the Nineties. Mandatory minimum sentences and three-strikes-and-you’re-out sentencing kept criminals in prison for longer. The war on drugs, especially the crack cocaine epidemic, sent a lot more people to prison. Guys who are locked up can’t commit crimes, at least not against ordinary citizens. (Fellow prisoners or guards? That’s another story.)

Inevitably, there is a down-side. First, the United States has one-twentieth of the world’s population, but one-fourth of the prison population. That includes both Russia and China. There are more people currently in prison in the United States (2.3 million) than there are in any one of fifteen states, and more than in the four least-populated states put together. The rate of imprisonment in the United States is the highest in the world.

Second, black communities have been particularly hard hit by both crime and punishment. One in nine black men between the ages of 20 and 34 is in jail. (The overall ratio of imprisoned to paroled/probationed is about 1:3, so that would suggest that another three in nine black men is under some other form of judicial supervision.) Since felons lose the right to vote, large numbers of blacks have been dis-franchised in what one law professor has labeled “the new Jim Crow.” Since most prisons are located in rural areas, this leads to the over-representation of areas unsympathetic to city problems.

Third, keeping huge numbers of prisoners locked up is really expensive. Americans don’t like to pay taxes, so prison budgets have been held down for decades. The result is massive over-crowding. Courts have repeatedly held this over-crowding to amount to cruel and unusual punishment.

Fourth, imprisonment doesn’t seem to do anything to change behavior. Says one criminologist, “two-thirds of those who leave prison will be back within three years.”

What have changed are the crime rates. Between 1991 and 2009, the number of murders fell by 45 percent. From its peak of 9.8/100,000 in 1991, the murder rate fell to 5.0/100,000 in 2009. The same decline has been found in most other categories of crime over the same period. At least for now.

Prisoners are so numerous that, if grouped together and represented in the Congress, they would be a formidable voting bloc.

“The prison nation,” The Week, 13 February 2009, p. 13; “The mystery of falling crime rates,” The Week, 16 July 2010, p. 13.