<human>: Steven David "Steve" Levitt (born May 29, 1967) is an American economist known for his work in the field of crime, in particular on the link between legalized abortion and crime rates. Winner of the 2003 John Bates Clark Medal, he is currently the William B. Ogden Distinguished Service Professor of Economics at the University of Chicago, director of the Becker Center on Chicago Price Theory at the University of Chicago Booth School of Business. He was co-editor of the Journal of Political Economy published by the University of Chicago Press until December 2007. With journalist Stephen J. Dubner, he co-authored the best-selling book Freakonomics (2005) and its sequels SuperFreakonomics (2009)

On April 10, 2006, John Lott filed suit for defamation against Steven Levitt and HarperCollins Publishers over the book Freakonomics and against Levitt over a series of emails to retired economist John B. McCall. In the book Freakonomics, Levitt and coauthor Stephen J. Dubner claimed that the results of Lott's research in More Guns, Less Crime had not been replicated by other academics. In the emails to McCall, who had pointed to a number of papers in different academic publications that had replicated Lott's work, Levitt wrote that the work by authors supporting Lott in a special 2001 issue of the Journal of Law and Economics had not been peer reviewed, alleged that Lott had paid the University of Chicago Press to publish the papers, and that papers with results opposite of Lott's had been blocked from publication in that issue.  A federal judge found that Levitt's replication claim in Freakonomics was not defamation but found merit in Lott's complaint over the email claims.  Levitt settled the second defamation claim by admitting in a letter to John B. McCall that he himself was a peer reviewer in the 2001 issue of the Journal of Law and Economics, that Lott had not engaged in bribery (paying for extra costs of printing and postage for a conference issue is customary), and that he knew that "scholars with varying opinions" (including Levitt himself) had been invited to participate. The Chronicle of Higher Education characterized Levitt's letter as offering "a doozy of a concession."  The dismissal of the first half of Lott's suit was unanimously upheld by The United States Court of Appeals for the Seventh Circuit on February 11, 2009. CANNOTANSWERAnswer this question using a quote from the following article:

what was Lott's work that led to the suit
<bot>: the book Freakonomics