Despite its reputation as a hive of gun-toting murderous maniacs, the United States has enjoyed a tremendous drop in crime over the past twenty years. The murder rate alone is half what it was two decades ago, but all types of crime have plummeted. What could be causing this unexpected long-term trend? Social scientists have proposed some pretty weird theories which could just be right.


The stereotype of Americans is that we are a violent lot, prone to shooting each other at random. And yet if you compare US crime rates to those in European countries, you can see that crime has been rising in Europe as it declines in the US.


Employment

During the last twenty years, the US has gone through periods of economic boom and bust. Could employment numbers be affecting crime statistics? In a study of the relationship between employment and crime, economist Rudolph Winter-Ebmer and public policy researcher Stephen Raphael note that the conventional wisdom has been that violent crime rises during economic boom times. Summarizing their findings, they write:

Much research up to now has concluded that violent crime, as opposed to burglary and theft, is pro-cyclical, or higher in good times . . . One prime candidate is alcohol consumption, which is higher in good times, but on the other hand is a hefty determinant of all sorts of crime rates.

More money means more booze, which means more crime. Makes sense.

Except that's not what the two researchers found. From 1992 to 1996, they explain, "a period when unemployment was falling, there was a dramatic fall in all types of crime." They conclude that "a drop of two percentage points in unemployment would mean a 9% decline in burglary, 14% in rape and robbery and 30% in assault." It's possible crime began to fall in the 1990s as our economic prospects brightened.


But in that case, shouldn't crime be rising now that so many people are unemployed and losing their homes? Not if you consider another crime deterrent . . .

Abortion

One of the most widely-cited articles about the decline of crime in America is by economist Steven D. Levitt, who carefully shreds most common-sense ideas about what alleviates crime. He's completely unimpressed by the idea that employment might have anything to do with the decline in crime. Instead, he proposes — among other things — that the US defeated crime by legalizing abortion. He writes:

The underlying theory rests on two premises: 1) unwanted children are at greater risk for crime, and 2) legalized abortion leads to a reduction in the number of unwanted births.


He points out that crime begins to decline in America roughly one generation after abortion was legalized. In other words, all those abortions in the 1970s may have helped prevent a generation of criminals who would have come of age in the 1990s.


Levitt also notes that the 1990s marked a steep rise in numbers of police as well as numbers of people in prison.

Nice Windows

In 1982, George Kelling and James Wilson wrote an incredibly influential article in The Atlantic that spawned what is today called "the broken windows theory" of crime. They wrote:

At the community level, disorder and crime are usually inextricably linked, in a kind of developmental sequence. Social psychologists and police officers tend to agree that if a window in a building is broken and is left unrepaired, all the rest of the windows will soon be broken. This is as true in nice neighborhoods as in rundown ones. Window-breaking does not necessarily occur on a large scale because some areas are inhabited by determined window-breakers whereas others are populated by window-lovers; rather, one unrepaired broken window is a signal that no one cares, and so breaking more windows costs nothing. (It has always been fun.) . . . We suggest that "untended" behavior also leads to the breakdown of community controls.


Inspired by examples of community-oriented policing in the article, New York city implemented a "broken windows" policy which emphasized stopping minor crimes like vandalism and jumping turnstiles to avoid paying subway fares. Indeed, New York City's crime rate fell faster than the rest of the nation during the 1990s. But was it just because they'd fixed the broken windows? Law professor Franklin Zimring points out that it could also be the fact that New York City increased the number of police department employees by 35 percent. Perhaps it's not keeping the windows nice, but also just having more police on the street? Levitt agrees with this idea, suggesting that along with abortion one crime deterrent is simply more police rather than "innovative policing strategies."

Social scientists studying the declining crime rate almost universally confess that there is no simple reason why the US crime rate is in freefall. It might have to do with employment and abortion, or it might have to do with the number of police on the street and people in prison. As with any social phenomenon, the causes are incredibly complex and constantly change over time. It's also hard to draw conclusions without a control group, though it is interesting to compare the US crime rate with Europe's, where there are far fewer people in jail. Zimring, however, notes that the Canadian crime rate has fallen along with the US crime rate, and Canada also has far fewer prisoners than the US.


All we know for certain is that the US crime rate is falling, and it has continued to fall right up to the present day. We may not be able to understand all the factors involved until crime starts rising again, at which point we can investigate what has changed.

All sources linked in the text.