November 29, 2005

Abortion and crime: So, Levitt was wrong. But, what actually happened?

Now that Freakonomics author Steven D. Levitt's mishandling of his abortion-crime data has been exposed by economist Christopher Foote, I'd like to review what actually happened in American over those decades.

As I tried to explain to Dr. Levitt when we debated in Slate in 1999, what happened, simplifying greatly, was that the vast youth crack crime wave took off first in later 1980s in the socially liberal states where legal abortion also had taken off first about 17 years earlier, most notably New York and California, which legalized abortion in 1970, three years before Roe v. Wade.

In other words, there was at the state level, a positive correlation (when appropriately weighted by population of state), between the legal abortion rate in the early 1970s and the homicide offending rate in the late 1980s and early 1990s among those youths born after legalization, not the negative correlation asserted by Dr. Levitt. Unfortunately, Dr. Levitt initially only looked at crime rates in the years 1985 and 1997 (and only looked at the overly crude age groups of over and under 25), so he completely missed how his theory had catastrophically failed its most obvious historical test.

Second, and also contrary to Levitt's theory, this vast youth murder wave took off first specifically in the demographic group that had the highest legal abortion rate: urban blacks. The non-white abortion rate peaked in 1977, well before the peak of the white abortion rate. The peak years for homicide among 14-17 year old black males were 1993 and 1994 -- i.e., the cohort born at the peak of the black usage of legal abortion. As Donohue and Levitt wrote in 2001, under their theory, the opposite was supposed to happen:

"“Fertility declines for black women are three times greater than for whites (12 percent compared to 4 percent). Given that homicide rates of black youths are roughly nine times higher than those of white youths, racial differences in the fertility effects of abortion are likely to translate into greater homicide reductions."

Instead, among black males born in the late 1970s, their murder rate among 14-17 year olds was four times higher than among black males born in the late 1960s, before the legalization of abortion. The black to white teen murder rate ratio almost doubled after legalization. So, the Levitt-Donohue theory failed its first two historical tests in a disastrous fashion.

Then, two things happened historically that helped create the (presumably, assuming Foote's new technical critique doesn't completely eliminate it) state-level negative correlation between later 1970s abortion rates and later 1990s crime rates that Levitt and Donohue have emphasized so repeatedly, while trying to cover up the earlier negative correlation. (They imply that the longer the time lag between presumed cause and effect, the more trust we should put in it!)

1. From NY and CA, crack spread to more socially conservative states, where the abortion rate had also gone up later. So crime was higher in the mid to late 1990s in socially conservative states where abortion rates didn't go up until the late 1970s or early 1980s.

2. And, the crack wave burned out first in the places where it started first, most famously New York City.

We've all heard a million arguments about why crime fell in NYC in the 1990s, but an overlooked explanation was brought up by Knight-Ridder reporter Jonathan Tilove recently: there are today in NYC, 36% more black women alive than black men. Nationally, among all races, there are 8% more women than men alive.

Obviously, this gigantic black male shortage in NYC wasn't caused by abortion -- there was virtually no sex selective abortion at the time. No, it was mostly caused by an enormous increase in imprisonment and by the most dangerous black men murdering each other in large quantities in the late 1980s and early 1990s. (AIDS played a role too.) Levitt has never written, as far as I know, about the impact of these "selective post-natal abortions," as it were, on the crime rate, but it's clearly a substantial factor in a number of big cities that were hit hard by crack. (NYC is by no means unique in terms of the current black male shortage.)

Moreover, as I pointed out to Levitt in 1999, and as his deservedly famous chapter in "Freakonomics" on how dealing crack pays so badly confirmed, a lot of the next cohort of urban youths, those born more than a half decade after abortion was legalized in their state, figured out that dealing crack was a stupid career choice. Seeing how their older brothers and cousins were winding up in prisons, wheelchairs, and cemeteries, they became less likely to commit murder. Participating in the crack wars were, for the vast majority of the gangstas, extremely bad life choices, and it's hardly surprising that the later cohort born in the early 1980s did a better job of figuring this out.

But these anti-crime trends in the 1990s happened first where crack happened first, which tended to also be where legal abortion happened first, thus creating the most likely spurious correlation between legal abortion and the crime decline in the later 1990s that Freakonomics focuses upon.

So, for this controversy, the crucial issue is The Burden of Proof. Dr. Levitt has tried hard to hand the burden of proof off to his skeptics, claiming that he's looked at all other possible causes of the 1990s crime decline, and they aren't adequate to explain it, so abortion must be the cause of the remainder. That's a weak and irresponsible argument.

Of course, in reality, he hasn't looked at all the causes -- for example, I've never seen him take into account "selective post-natal abortions" of the most dangerous gangstas by other gangstas, nor the social learning impact on the next cohort of seeing their older brothers die or go to prison.

But, moreover, there's an old saying that large assertions require large evidence. And Levitt's abortion-cut-crime theory is one of the largest assertions in the social sciences in recent years. Clearly, the burden of proof rests on Dr. Levitt.

There's also an old idea in science called Occam's Razor, which more or less says that scientists should be biased toward simplicity in explanations. Throughout this six year controversy, Dr. Levitt has consistently gone for the most complicated, hard-to-understand, and (as we've seen this week, to Dr. Levitt's embarrassment) hard-to-check-up-on statistical models.

In contrast, he's combined statistical incomprehensibility with the most simple-minded behavioral models -- he has repeatedly assumed, despite all the evidence from American studies cited above, that ghetto women decide whether or not to engage in unprotected sex and whether or not get an abortion or have an illegitimate child for the same reasons that would appeal to highly educated women of his own class. While Levitt's style of thinking about how women respond to legalized abortion has proven highly persuasive to the nonfiction book purchasing class, it doesn't explain much at all about the behavior of the class in which potential criminals are typically raised.

Maybe the technical opacity of Dr. Levitt's analysis was necessary -- social phenomena are terribly complicated. But the impact of his behavior on the public and on much of his profession has been to encourage among his numberous fans not a critical engagement with the historical and sociological record, but an attitude of faith, a warm feeling that this really smart guy has Figured It All Out using Really Complicated Statistics and we should just take his word for it.

As a marketing strategy, the oracular approach of "Freakonomics" has been mind-bogglingly successful, but perhaps I may be forgiven for wondering whether it advances the cause of good social science.

All the data cited above can be found documented at


My published articles are archived at -- Steve Sailer

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