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news and the national conversation.

When the crime rate began falling in the early 1990s, it did so with such speed

and suddenness that it surprised everyone. It took some experts many years to

even recognize that crime was falling, so confident had they been of its

continuing rise. Long after crime had peaked, in fact, some of them continued to

predict ever darker scenarios. But the evidence was irrefutable: the long and

brutal spike in crime was moving in the opposite direction, and it wouldn’t stop

until the crime rate had fallen back to the levels of forty years earlier.

Now the experts hustled to explain their faulty forecasting. The criminologist

James Alan Fox explained that his warning of a “blood-bath” was in fact an

intentional overstatement. “I never said there would be blood flowing in the

streets,” he said, “but I used strong terms like ‘bloodbath’ to get people’s

attention. And it did. I don’t apologize for using alarmist terms.” (If Fox seems to

be offering a distinction without a difference—“bloodbath” versus “blood

flowing in the streets”—we should remember that even in retreat mode, experts

can be self-serving.)

After the relief had settled in, after people remembered how to go about their

lives without the pressing fear of crime, there arose a natural question: just where

did all those criminals go?

At one level, the answer seemed puzzling. After all, if none of the criminologists,

police officials, economists, politicians, or others who traffic in such matters had

foreseen the crime decline, how could they suddenly identify its causes?

But this diverse army of experts now marched out a phalanx of hypotheses to

explain the drop in crime. A great many newspaper articles would be written on

the subject. Their conclusions often hinged on which expert had most recently

spoken to which reporter. Here, ranked by frequency of mention, are the crime-

drop explanations cited in articles published from 1991 to 2001 in the ten largest-

circulation papers in the LexisNexis database:

CRIME-D ROP EXPLANATION

NUMBER OF

CITATIONS

1. Innovative policing strategies

52

2. Increased reliance on prisons

47

3. Changes in crack and other drug markets

33

4. Aging of the population

32

5. Tougher gun control laws

32

6. Strong economy

28

7. Increased number of police

26

8. All other explanations (increased use of capital

punishment, concealed-weapons laws, gun buybacks, and

others)

34

If you are the sort of person who likes guessing games, you may wish to spend

the next few moments pondering which of the preceding explanations seem to

have merit and which don’t. Hint: of the seven major explanations on the list,

only three can be shown to have contributed to the drop in crime. The others are,

for the most part, figments of someone’s imagination, self-interest, or wishful

thinking. Further hint: one of the greatest measurable causes of the crime drop

does not appear on the list at all, for it didn’t receive a single newspaper

mention.

Let’s begin with a fairly uncontroversial one: the strong economy. The decline in

crime that began in the early 1990s was accompanied by a blistering national

economy and a significant drop in unemployment. It might seem to follow that

the economy was a hammer that helped beat down crime. But a closer look at the

data destroys this theory. It is true that a stronger job market may make certain

crimes relatively less attractive. But that is only the case for crimes with a direct

financial motivation—burglary, robbery, and auto theft—as opposed to violent

crimes like homicide, assault, and rape. Moreover, studies have shown that an

unemployment decline of 1 percentage point accounts for a 1 percent drop in

nonviolent crime. During the 1990s, the unemployment rate fell by 2 percentage

points; nonviolent crime, meanwhile, fell by roughly 40 percent. But an even

bigger flaw in the strong-economy theory concerns violent crime. Homicide fell

at a greater rate during the 1990s than any other sort of crime, and a number of

reliable studies have shown virtually no link between the economy and violent

crime. This weak link is made even weaker by glancing back to a recent decade,

the 1960s, when the economy went on a wild growth spurt—as did violent crime.

So while a strong 1990s economy might have seemed, on the surface, a likely

explanation for the drop in crime, it almost certainly didn’t affect criminal

behavior in any significant way.

Unless, that is, “the economy” is construed in a broader sense—as a means to

build and maintain hundreds of prisons. Let’s now consider another crime-drop

explanation: increased reliance on prisons. It might help to start by flipping the

crime question around. Instead of wondering what made crime fall, think about

this: why had it risen so dramatically in the first place?

During the first half of the twentieth century, the incidence of violent crime in the

United States was, for the most part, fairly steady. But in the early 1960s, it began

to climb. In retrospect, it is clear that one of the major factors pushing this trend

was a more lenient justice system. Conviction rates declined during the 1960s,

and criminals who were convicted served shorter sentences. This trend was

driven in part by an expansion in the rights of people accused of crimes—a long

overdue expansion, some would argue. (Others would argue that the expansion

went too far.) At the same time, politicians were growing increasingly softer on

crime—“for fear of sounding racist,” as the economist Gary Becker has written,

“since African-Americans and Hispanics commit a disproportionate share of

felonies.” So if you were the kind of person who might want to commit a crime,

the incentives were lining up in your favor: a slimmer likelihood of being

convicted and, if convicted, a shorter prison term. Because criminals respond to

incentives as readily as anyone, the result was a surge in crime.

It took some time, and a great deal of political turmoil, but these incentives were

eventually curtailed. Criminals who would have previously been set free—for

drug-related offenses and parole revocation in particular—were instead locked

up. Between 1980 and 2000, there was a fifteenfold increase in the number of

people sent to prison on drug charges. Many other sentences, especially for

violent crime, were lengthened. The total effect was dramatic. By 2000, more than

two million people were in prison, roughly four times the number as of 1972.

Fully half of that increase took place during the 1990s.

The evidence linking increased punishment with lower crime rates is very

strong. Harsh prison terms have been shown to act as both deterrent (for the

would-be criminal on the street) and prophylactic (for the would-be criminal

who is already locked up). Logical as this may sound, some criminologists have

fought the logic. A 1977 academic study called “On Behalf of a Moratorium on

Prison Construction” noted that crime rates tend to be high when imprisonment

—an act that, in his

confused mind, will ensure a victory.

rates are high, and concluded that crime would fall if imprisonment rates could

only be lowered. (Fortunately, jailers did not suddenly turn loose their wards

and sit back waiting for crime to fall. As the political scientist John J. DiIulio Jr.

later commented, “Apparently, it takes a Ph.D. in criminology to doubt that

keeping dangerous criminals incarcerated cuts crime.”) The “Moratorium”

argument rests on a fundamental confusion of correlation and causality.

Consider a parallel argument. The mayor of a city sees that his citizens celebrate

wildly when their team wins the World Series. He is intrigued by this correlation

but, like the “Moratorium” author, fails to see the direction in which the

correlation runs. So the following year, the mayor decrees that his citizens start

celebrating the World Series before the first pitch is thrown

There are certainly plenty of reasons to dislike the huge surge in the prison

population. Not everyone is pleased that such a significant fraction of Americans,

especially black Americans, live behind bars. Nor does prison even begin to

address the root causes of crime, which are diverse and complex. Lastly, prison is

hardly a cheap solution: it costs about $25,000 a year to keep someone

incarcerated. But if the goal here is to explain the drop in crime in the 1990s,

imprisonment is certainly one of the key answers. It accounts for roughly one-

third of the drop in crime.

Another crime-drop explanation is often cited in tandem with imprisonment: the

increased use of capital punishment. The number of executions in the United

States quadrupled between the 1980s and the 1990s, leading many people to

conclude—in the context of a debate that has been going on for decades—that

capital punishment helped drive down crime. Lost in the debate, however, are

two important facts.

First, given the rarity with which executions are carried out in this country and

the long delays in doing so, no reasonable criminal should be deterred by the

threat of execution. Even though capital punishment quadrupled within a

decade, there were still only 478 executions in the entire United States during the

1990s. Any parent who has ever said to a recalcitrant child, “Okay, I’m going to

count to ten and this time I’m really going to punish you,” knows the difference

between deterrent and empty threat. New York State, for instance, has not as of

this writing executed a single criminal since reinstituting its death penalty in

1995. Even among prisoners on death row, the annual execution rate is only 2

percent—compared with the 7 percent annual chance of dying faced by a

member of the Black Gangster Disciple Nation crack gang. If life on death row is

safer than life on the streets, it’s hard to believe that the fear of execution is a

driving force in a criminal’s calculus. Like the $3 fine for late arriving parents at

the Israeli day-care centers, the negative incentive of capital punishment simply

isn’t serious enough for a criminal to change his behavior.

The second flaw in the capital punishment argument is even more obvious.

Assume for a moment that the death penalty is a deterrent. How much crime

does it actually deter? The economist Isaac Ehrlich, in an oft-cited 1975 paper,

put forth an estimate that is generally considered optimistic: executing 1 criminal

translates into 7 fewer homicides that the criminal might have committed. Now

do the math. In 1991, there were 14 executions in the United States; in 2001, there

were 66. According to Ehrlich’s calculation, those 52 additional executions would

have accounted for 364 fewer homicides in 2001—not a small drop, to be sure,

but less than 4 percent of the actual decrease in homicides that year. So even in a

death penalty advocate’s best-case scenario, capital punishment could explain

only one twenty-fifth of the drop in homicides in the 1990s. And because the

death penalty is rarely given for crimes other than homicide, its deterrent effect

cannot account for a speck of decline in other violent crimes.

It is extremely unlikely, therefore, that the death penalty, as currently practiced

in the United States, exerts any real influence on crime rates. Even many of its

onetime supporters have come to this conclusion. “I feel morally and

intellectually obligated simply to concede that the death penalty experiment has

failed,” said U.S. Supreme Court Justice Harry A. Blackmun in 1994, nearly

twenty years after he had voted for its reinstatement. “I no longer shall tinker

with the machinery of death.”

So it wasn’t capital punishment that drove crime down, nor was it the booming

economy. But higher rates of imprisonment did have a lot to do with it. All those

criminals didn’t march into jail by themselves, of course. Someone had to

investigate the crime, catch the bad guy, and put together the case that would get

him convicted. Which naturally leads to a related pair of crime-drop

explanations:

. Innovative policing strategies

. Increased number of police

Let’s address the second one first. The number of police officers per capita in the

United States rose about 14 percent during the 1990s. Does merely increasing the

number of police, however, reduce crime? The answer would seem obvious—

yes—but proving that answer isn’t so easy. That’s because when crime is rising,

people clamor for protection, and invariably more money is found for cops. So if

you just look at raw correlations between police and crime, you will find that

when there are more police, there tends to be more crime. That doesn’t mean, of

course, that the police are causing the crime, just as it doesn’t mean, as some

criminologists have argued, that crime will fall if criminals are released from

prison.

To show causality, we need a scenario in which more police are hired for reasons

completely unrelated to rising crime. If, for instance, police were randomly

sprinkled in some cities and not in others, we could look to see whether crime

declines in the cities where the police happen to land.

As it turns out, that exact scenario is often created by vote-hungry politicians. In

the months leading up to Election Day, incumbent mayors routinely try to lock

up the law-and-order vote by hiring more police—even when the crime rate is

standing still. So by comparing the crime rate in one set of cities that have

recently had an election (and which therefore hired extra police) with another set

of cities that had no election (and therefore no extra police), it’s possible to tease

out the effect of the extra police on crime. The answer: yes indeed, additional

police substantially lower the crime rate.

Again, it may help to look backward and see why crime had risen so much in the

first place. From 1960 to 1985, the number of police officers fell more than 50

percent relative to the number of crimes. In some cases, hiring additional police