From APM, American Public Media, and WNYC.

This is Freakonomics Radio on Marketplace.

Here's the host of Marketplace, Kyra's Doll.

It's time once again for a little bit of Freakonomics Radio.

Every couple of weeks we talk to Stephen Dubner,

the co-author of the books and the blog of the same name.

Join this week by the other guy, the other co-author,

Stephen Levin from the University of Chicago.

Guys, welcome to the program.

Hey, Ky, how are you? Good to be here.

Okay, so the topic of the tour is cheating,

specifically teacher cheating.

There have been some big scandals lately in Atlanta,

and I think in Washington, D.C.

And Levin in Chicago, like eight or ten years ago,

you actually caught some teacher cheating.

So the first question is based on your experience,

can we say how many teachers cheat?

Looking at the data, our estimate at the time,

we thought that 5% of all the elementary school classrooms

in Chicago showed evidence that the teachers had cheated

on behalf of their students on these exams.

...