PW: At the beginning of Freakonomics, you talk about the reluctance you felt when publishers first approached you about writing a book. Why was that?

Steven Levitt: I'm not a very good writer, and I didn't feel that I could do an adequate job of communicating my ideas to a broader audience. Also, I've generally not liked nonacademic books that attempt to talk about academic ideas. What turned me was that somebody gave me a copy of The Tipping Point. I loved it, and I thought Malcolm Gladwell did such a fantastic job of melding beautiful writing and interesting questions with solid academics that it made me think it would be possible—not by myself, but with someone like Stephen Dubner—to do a book that was really first-rate.

PW: When did Stephen Dubner go from interviewer [for a New York Times profile] to collaborator?

SL: I felt like he and I had such a rapport. He was so smart in interviewing me originally, and knew my work so well, that I had total confidence we would work as a fantastic team. And we just really clicked. There's a lighthearted, irreverent tone to Freakonomics, which I think captures the fun we had writing it.

PW: Money is not the primary focus of your work. What was it that first got you interested in economics?

SL: I had no intrinsic interest in it until I took an introductory course and realized that I had always been an economist. When they put concepts up on the board, I'd think, "So that's the name for what I've always thought." I was just born thinking like an economist who was more interested in issues like crime and corruption and race and social issues. My opinion has always been that economics got dealt a very powerful set of tools for understanding complex systems and a very boring set of questions. So what I've tried to do is take these great tools and use them on questions that are more fun, more interesting, but have often been regarded as questions for psychology or sociology.

PW:The aspect of fun is probably the most surprising thing about the book—that not all of the questions you address involve depressing statistics.

SL: Whatever comes my way, if I think I can say something interesting about it, I'll go after it. The baby names question, for example, came up when I took my undergrad students to an inner-city high school for a day. I remember looking through the yearbook and noticing that I couldn't find any two girls in the entire high school who shared the same name. It struck me as an amazing puzzle, why black names and white names are so different. So when I stumbled onto the data set with all the birth certificates and first names, it was an idea that had been percolating for almost a decade. It turned out to be even more interesting than I'd suspected, because it went far beyond black and white names into the class side of naming.

PW: We noticed your youngest daughter has one of the names you predict will be extremely popular in 2015.

SL: As we were getting ready to adopt Sophie, I showed my wife that list—I didn't tell her what it was, I just said it was a list of really interesting names, and I was delighted that she picked one of them. It's almost an inside joke, except that I think my wife still doesn't know what the list is. When she finds out, I'm probably going to be in trouble.