A number of people have asked me what I think of the bestselling book "Freakonomics" written by Steven Levitt and Stephen Dubner. On the front of the book, there is a glowing blurb by me which would suggest that I love it. On the other hand, chapter four of Freakonomics is devoted to the question of why crime dropped so dramatically in America—and particularly New York—in the 1990’s, and in that chapter Dubner and Levitt reach a very different conclusion than I do in "The Tipping Point." In fact, "Freakonomics" specially singles out for ridicule the theory of broken windows, which I suggest in the Tipping Point played a big role in New York City’s recovery. So what gives? Why do I love a book so much, if it contradicts my own book? Have I renounced the theories I put forward in the Tipping Point?

I have two answers. The first—obvious—point is that it is not necessary to agree with everything you read in a book to like that book. I have a number of problems with several chapters in Freakonomics, because I find the way in which economists approach problems occasionally frustrating. That being said, it’s very difficult to read Freakonomics and not find yourself saying "wow" every five minutes. I loved it.

Now for the long answer: what do I think of the substance of their crime argument? Is the Broken Windows theory central to the question of whether crime dropped, or isn’t it?

The Freakonomics argument starts off very much like the argument I make in The Tipping Point. The startling decline in crime in major American cities in the mid-1990’s is a mystery. No one predicted it. Everyone thought that high crime rates were a permanent feature of urban life. And the standard arguments to explain why crime falls don’t seem to work in this case. Levitt and Dubner go through all the usual explanations for crime decreases—a booming economy, decline in the crack trade, innovative policing strategies, tougher gun laws, aging of the population—and find only two that they think really matter. Putting more police on the street, they say, which happened in major cities all over the country in the early 1990’s, was a major factor. So were the soaring numbers of young men put away in prison in that same period. But neither of those two factors, they argue, are sufficient to explain the full magnitude of the crime drop. There has to be something else—and their candidate for the missing explanation is the legalization of abortion.

Levitt’s argument (and for simplicity’s sake, I’ll refer to the argument from now on as Levitt’s) goes something like this (and keep in mind that I’m grossly simplifying it here). The huge declines in urban violent crime rates happen, more or less, eighteen years after the passage of Roe v. Wade. States that legalized abortion earlier than the Supreme Court ruling saw their violent crime rates fall earlier. When you look at falling crime rates, the reductions in violent behavior are almost all concentrated in the generation born after the legalization of abortion, not before. People undergo abortions, in other words, for a reason: because they are poor, or don’t want a child, or live in an environment where it is hard to raise children. An unwanted child has a higher chance, when he or she grows up, of becoming a criminal. By removing a large number of unwanted children, legalized abortion ended up lowering the crime rate. Levitt makes it clear that he’s not passing judgment on this. He’s not pro-abortion, as a result of this observation. He’s just explaining the way he thinks the world works. He also stresses—and this is because even more important—that he doesn’t think that crime fell in major American cities solely because of abortion. He thinks abortion is simply one of several factors—albeit a significant one—in the crime drop.

Is Levitt right that legalizing abortion has played a role in lowering violent crime rates? Levitt has a few critics, and he’s dealt with them pretty effectively, I think. (Check out Freakonomics.com) There are some other technical critiques of his work from fellow economists, that, I have to confess, I can’t follow. My own response is chiefly that I find the argument incomplete.. For instance, the biggest drop in fertility in the U.S. came with the advent of the Pill in the mid-1960’s. The Pill allowed lots of women who would otherwise have become pregnant not to become pregnant because they were poor, or didn’t want a child, or lived in an environment where it was hard to raise children. But the fertility drop caused by the Pill didn’t lead to a decrease in crime eighteen years later. In fact, that generation saw a massive increase in crime. The advent of abortion in the early 1970’s, meanwhile, caused a far, far smaller drop in U.S. fertility but—Levitt argues—that drop is consistent with a fall in crime. In other words, the unwanted children whose births were prevented by the Pill would not have gone to become criminals. But unwanted children whose births were prevented by abortion would have gone on become criminals. Why is this? I can think of some hypotheses. But they are just that: hypotheses. I would have been a lot happier with Freakonomics if the crime chapter had been twice as long—and spent more time explaining just what is so peculiar, in terms of crime rates, about births prevented by abortion.

But that’s a quibble. In the course of making his argument for the importance of abortion Levitt is also pretty dismissive of other, alternate, theories—especially the theory that I spend a lot of time on the Tipping Point, namely the broken windows idea.

It’s here, though, where I think Levitt’s argument is a bit unfair. Levitt concludes that there are three factors that matter the most in the crime drop—abortion, high rates of imprisonment of young men, and increased number of police officers. The last of these three factors he glosses over pretty quickly. But I think that’s a mistake, because what is increased police presence? Well, having more police on the streets than before means that law enforcement can be more aggressive and pro-active. It means officers can do a lot better job getting guns off the streets. It means that they can be much more vigilant than before. It means that they have the time and resources to start cracking down on the kinds of seemingly minor "lifestyle" crimes than might have gone ignored before. The kinds of things that I argue were so important in responding a civil environment in New York State—the crackdowns on graffiti and public urination and panhandling and turnstile jumping in the subway system—are all the kinds of things that police departments can do when they have more officers on the streets. In Freakonomics, Levitt pretends he has refuted the Broken Windows explanation. He hasn’t at all. In fact, to the extent that he concedes the huge role played by the expansion of police departments in the 1990’s, he tacitly supports the Broken Windows theory.

So why is he so anxious to discredit Broken Windows? One—understandable—explanation is that he makes his own argument more compelling by dismissing all other arguments. (I know all about this tactic. I do it all the time). But a deeper explanation, I think, has to do with the difference between the perspective of economics and the perspective of psychology. Levitt is very interested in the root causes of behavior, in the kinds of incentives and circumstances that fundamentally shape the way human beings act. That’s the kind of thing that economists—particularly behavioral economists—think a lot about. And rightly so: who we are and how we behave is a product of forces and influences rooted in the histories and traditions and laws of the societies in which we belong.

But there’s a second dimension to crime, and that is the immediate contextual influences on human behavior. If you talk to a police officer (or a psychologist) they’ll tell you what a "typical" murder looks like. It’s two men, drunk at a bar. They get in a fight. They step outside. One pulls a gun in anger and kills the other. You can prevent that homicide by creating a population of people who are less likely to get drunk and angry in bars. You can also prevent that homicide by decreasing the likelihood of either of those drunken men having a gun. Police-work is concerned, necessarily, with this kind of immediate influence on behavior, and one of the things that having lots more police did was to make it possible to reduce the number of guns on the street that could end as a cause for a homicide. Drunken young men still fight in bars in New York City. But now they fight with fists—which are a lot safer.

Freakonomics is a book about deeply rooted influences on behavior, because it’s a book written by an economist. The Tipping Point is a book, by contrast, about the kinds of things that law enforcement types—and psychologists—worry about, because it was written by someone who is obsessed with psychology. I prefer to think of Freakonomics not as contradicting my argument in Tipping Point, but as completing it.

One final point (just to complicate things even further). Since Tipping Point has come out, there have been a number of economists who have looked specifically at broken windows—and tried to test the theory directly. Some have found support for it. Others—particularly Bernard Harcourt at the University of Chicago—find it wanting. If you crave a rigorous critique of broken windows, read Harcourt. He’s every bit as smart as Levitt.