[Paleopsych] WSJ: When Numbers Solve a Mystery

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Sat Apr 16 22:45:43 UTC 2005

When Numbers Solve a Mystery
Meet the economist who figured out that legal abortion was behind
dropping crime rates.


Wednesday, April 13, 2005 12:01 a.m.

If Indiana Jones were an economist, he'd be Steven Levitt. The most
recent winner of the John Bates Clark award for the best economist under
the age of 40, Mr. Levitt is famous not as a master of dry technical
arcana but as a maverick treasure hunter who relies for success on his
wit, pluck and disregard for conventional wisdom. Mr. Levitt's typical
quarry is hidden not in some exotic locale but in a pile of data. His
genius is to take a seemingly meaningless set of numbers, ferret out the
telltale pattern and recognize what it means.

It was Mr. Levitt who nailed a bunch of Chicago public-school teachers
for artificially inflating their students' standardized test scores. I'm
dying to tell you exactly how he did it, but I don't want to spoil any
surprises. His account of the affair in "Freakonomics" reads like a
detective novel.

The evidence is right there in front of you: Mr. Levitt actually
reproduces all the answer sheets from two Chicago classrooms and
challenges you to spot the cheater. Then he shows you how it's done. He
points to suspicious patterns that you almost surely overlooked.
Suspicious, yes, but not conclusive--maybe there is some legitimate
explanation. Except that Mr. Levitt slowly piles pattern on pattern,
ruling out one explanation after another until only the most insidious
one remains. The resulting tour de force is so convincing that it
eventually cost 12 Chicago schoolteachers their jobs.

The Case of the Cheating Teachers would make a fascinating book, but in
Mr. Levitt's hands it is compressed into 12 breathtaking pages. Then he
is on to his next adventure--the Case of the Cheating Sumo Wrestlers.
Here an entirely different kind of data (the win-loss records from
tournaments) gets the Levitt treatment: the identification of a
suspicious pattern, a labyrinth of reasoning to rule out the innocent
explanations and a compelling indictment.

Then it's on to another question, and another and another. Were
lynchings, as their malevolent perpetrators hoped, an effective way to
keep Southern blacks "in their place"? Do real-estate agents really
represent their clients' interests? Why do so many drug dealers live
with their mothers? Which parenting strategies work and which don't?
Does a good first name contribute to success in life?

Mr. Levitt is hardly the first to attack these questions; there is no
end of books on parenting strategy, for example. The difference is that
Mr. Levitt knows what he is talking about. Where other parenting books
rely on either puerile psychological theorizing or leaps of logic from
haphazard numerical correlations, Mr. Levitt relies on his instinct for
analyzing data. As a result, there is more valuable parenting advice in
Mr. Levitt's single chapter than in all the rest of Barnes & Noble. And
some of it is going to shock you. One example: It turns out that reading
to your children has no appreciable effect on their academic success.

Back in 1999, Mr. Levitt was trying to figure out why crime rates had
fallen so dramatically in the previous decade. He was struck by the fact
that crime began falling nationwide just 18 years after the Supreme
Court effectively legalized abortion. He was struck harder by the fact
that in five states crime began falling three years earlier than it did
everywhere else. These were exactly the five states that had legalized
abortion three years before Roe v. Wade.

Did crime fall because hundreds of thousands of prospective criminals
had been aborted? Once again, the pattern by itself is not conclusive,
but once again Mr. Levitt piles pattern on pattern until the evidence
overwhelms you. The bottom line? Legalized abortion was the single
biggest factor in bringing the crime wave of the 1980s to a screeching

Mr. Levitt repeatedly reminds us that economics is about what is true,
not what ought to be true. To this reviewer's considerable delight, he
cheerfully violates this principle at the end of the abortion discussion
by daring to address the question of whether abortion ought to be legal
or, more precisely, whether the effect on crime rates is a sufficient
reason to legalize abortion. He doesn't pretend to settle the matter,
but in just a few pages he constructs exactly the right framework for
thinking about it and then leaves the reader to draw his own

Economists, ever wary of devaluing their currency, tend to be stinting
in their praise. I therefore tried hard to find something in this book
that I could complain about. But I give up. Criticizing "Freakonomics"
would be like criticizing a hot fudge sundae. I had briefly planned to
gripe about the occasional long and pointless anecdotes, but I changed
my mind. Sure, we get six pages on the Chicago graduate student who
barely escaped with his life after his adviser sent him into the housing
projects with a clipboard to survey residents on how they feel about
being black and poor. Sure, there is no real point to the story. But a
story that good doesn't need a point.

The cherry on top of the sundae is Mr. Levitt's co-author, Stephen
Dubner, a journalist who clearly understands what he is writing about
and explains it in prose that has you chuckling one minute and gasping
in amazement the next. Mr. Dubner is a treasure of the rarest sort; we
are fortunate that Mr. Levitt managed to find him. I think I detect a

Mr. Landsburg, an economics professor at the University of Rochester, is
the author of "Armchair Economist: Economics and Everyday Experience."
You can buy "Freakonomics" from the OpinionJournal bookstore.

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