From 1991 to 2001, violent crime in the U.S. fell more than 30%, a decline not seen since the end of Prohibition. Steve Levitt — an economist at the University of Chicago and my Freakonomics friend and co-author — wanted to figure out why, after rising for thirty years, crime had suddenly started to decline.
Levitt explored all the commonly suggested reasons in a paper called “Understanding Why Crime Fell in the 1990s: Four Factors That Explain the Decline and Six That Do Not.” The six factors that, according to Levitt’s analysis, did not contribute to the crime drop: a strengthening economy; the aging of the population; innovative policing strategies; gun control laws; right to carry laws; and the increased use of capital punishment. While each of these, in theory, might seem to have some explanatory power, Levitt found that none of them did. The relationship between violent crime and the greater economy, for instance, is very weak. Capital punishment, he found, at least as currently practiced in the U.S., simply didn’t act as a deterrent against future crimes.
Then there were the factors he found did contribute: the increase in the number of police; an increase in the number of criminals imprisoned; and the decline of the crack-cocaine trade, which had been unusually violent. But these three factors could explain only about half of the massive drop in crime. It was as if there was some mysterious force that all the politicians and criminologists and journalists weren’t thinking about at all.
One day, paging through the Statistical Abstract of the United States (which is the kind of thing that economists like Levitt do for fun), he saw a number that shocked him. Abortion rose so much after Roe v. Wade that by its peak (in 1990), there were 1.5 million abortions a year in the U.S. compared to 4 million live births. The magnitude surprised Levitt, and he wondered what sort of secondary effects it might have. He wondered, for instance, if it might somehow be connected to the huge drop in crime. Levitt spent a few weeks working on the idea before ultimately deciding it didn’t quite add up.
Then one of Levitt’s collaborators, John Donohue, a professor of law at Stanford Law School who also has a PhD. in economics, mentioned that he, too, had wondered if the legalization of abortion may have reduced crime in the 1990s. Donohue was particularly interested in criminal justice issues — gun policy, sentencing guidelines, things like that.
“I walked him through my logic, ” Levitt says. “I had been focusing on the fact that when abortion became legal, there was a reduction in the number of children born. And John said, ‘Yeah, but what about unwantedness?’”
Donohue was referring to the expansive social-sciences literature showing that children born to parents who didn’t truly want that child, or weren’t ready for that child, were more likely to have worse outcomes as they grew up. Not only were health and education outcomes worse, but these so-called “unwanted” kids were disproportionately likely to engage in criminal behaviors.
Donohue had begun to put the puzzle together when he attended a conference and heard a paper presented by the economist Rebecca Blank. She discussed the characteristics of the women most likely to get an abortion after Roe v. Wade — poor, young, unmarried, inner-city, minority — and Donohue noticed that there was quite a bit of overlap between that population and the population of the criminals responsible for the rising crime rates.
Levitt and Donohue spent some time doing back-of-the-envelope calculations as to how significant this effect could be. The numbers were shocking. Remember, the magnitude of abortion was huge: at its peak, there were 345 abortions for every 1,000 live births. The mechanism was pretty simple: unwanted children were more likely than average to engage in crime as they got older; but an unwanted child who was never born would never have the opportunity to enter his criminal prime, 15 or 20 years later. Donohue and Levitt created a tidy syllogism: unwantedness leads to high crime; legalized abortion led to less unwantedness; therefore, abortion led to lower crime. But syllogisms are easy; what about evidence?
Levitt and Donohue, of course, couldn’t run a randomized, controlled trial to collect this evidence. So they set out to assemble a collage of evidence — in Levitt’s words, a set of “all quite imperfect sources of variation, that allow us to get some sense of whether there might be some causality between legalized abortion and crime.”
First, they utilized the variation produced by the fact that five states — New York, California, Washington, Alaska, and Hawaii — had legalized abortion before Roe. But those states aren’t particularly representative of the country as a whole. Given that limitation, Levitt and Donohue couldn’t just measure the crime rate in the early-legalizing states and compare them to the rest of the states. They needed another, more precise measurement. So they divided states into three groups: high abortion-rate states, medium abortion-rate states, and low abortion-rate states. Then they tracked crime in all three groups over time.
“We found that there was roughly a 30% difference in what had happened to crime between the highest abortion states and the lowest abortion states by 1997,” Levitt says.
That seemed to be firm evidence in support of the thesis. Donohue and Levitt next looked at crime data, state by state, by age of offender, comparing, for example, someone born in 1972 (before legalization) in Minnesota to someone born two years later.
“Because the abortion rates were rising so sharply in the ’70s, these cohorts were coming into their crime ages in a stacked fashion,” Donohue says. “And we could identify which abortion rates were associated with each particular age. And the higher the abortion rate was for each age, the greater the crime drop occurring.”
Levitt and Donohue would go on to publish their paper, “The Impact of Legalized Abortion on Crime,” in the May 2001 issue of The Quarterly Journal of Economics. “Legalized abortion,” they wrote, “appears to account for as much as 50 percent of the recent drop in crime.”
But even before the paper was published, their findings hit the news. As Levitt recalls, “everybody hated it.” Or, more precisely: “People who are in favor of right-to-life were upset because our argument seemed to be endorsing the idea that legalized abortion had positive effects. But people who believed in the right to choose were also upset because we were kind of saying, ‘Well, you’re killing these fetuses, so they never get a chance to grow up to be criminals.’ The number of death threats that I got from the left was actually greater than the number of death threats I got from the right.”
“Some people started to say that, you know, we were trying to go back to the times where people were pushing for control of the fertility of certain groups and maybe even racial groups,” Donohue says. “And that was certainly not anything that we even considered. We were just trying to figure out when public policy had changed in this profound way, did it alter the path of crime? We certainly weren’t eugenicists.”
“I actually think that our paper makes really clear why this has nothing to do with eugenics,” says Levitt. “ In our hypothesis, what happens is that abortion becomes legal; women are given the right to choose; and what our data suggests is that women are pretty good at choosing when they can bring kids in the world. And I think that’s such a fundamental difference — between women making good choices and eugenics, which is about the state, say, or some other entity forcing choices upon people, almost couldn’t be more different.”