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)
The impact of legalized abortion on crime
See The Impact of Legalized Abortion on Crime for a detailed discussion of the issue.  Revisiting a question first studied empirically in the 1960s, Donohue and Levitt argued that the legalization of abortion can account for almost half of the reduction in crime witnessed in the 1990s. This paper has sparked much controversy, to which Levitt has said  "The numbers we're talking about, in terms of crime, are absolutely trivial when you compare it to the broader debate on abortion. From a pro-life view of the world: If abortion is murder then we have a million murders a year through abortion. And the few thousand homicides that will be prevented according to our analysis are just nothing--they are a pebble in the ocean relative to the tragedy that is abortion. So, my own view, when we [did] the study and it hasn't changed is that: our study shouldn't change anybody's opinion about whether abortion should be legal and easily available or not. It's really a study about crime, not abortion."  In 2003, Theodore Joyce argued that legalized abortion had little impact on crime, contradicting Donohue and Levitt's results ("Did Legalized Abortion Lower Crime?" Journal of Human Resources, 2003, 38(1), pp. 1 -37.). In 2004, the authors published a response, in which they claimed Joyce's argument was flawed due to omitted-variable bias.  In November 2005, Federal Reserve Bank of Boston economist Christopher Foote and his research assistant Christopher Goetz, published a working paper, in which they argued that the results in Donohue and Levitt's abortion and crime paper were due to statistical errors made by the authors: the omission of state-year interactions and the use of the total number of arrests instead of the arrest rate in explaining changes in the murder rate. When the corrections were made, Foote and Goetz argued that abortion actually increased violent crime instead of decreasing it and did not affect property crime. They even concluded that the majority of women who had abortions in the 1970s were middle class whites rather than low income minorities as Levitt stated; this was, they stated, because white middle class women had the financial means for an abortion. The Economist remarked on the news of the errors that "for someone of Mr Levitt's iconoclasm and ingenuity, technical ineptitude is a much graver charge than moral turpitude. To be politically incorrect is one thing; to be simply incorrect quite another." In January 2006, Donohue and Levitt published a response, in which they admitted the errors in their original paper but also pointed out Foote and Goetz's correction was flawed due to heavy attenuation bias. The authors argued that, after making necessary changes to fix the original errors, the corrected link between abortion and crime was now weaker but still statistically significant, contrary to Foote and Goetz's claims. Foote and Goetz, however, soon produced a rebuttal of their own and showed that even after analyzing the data using the methods that Levitt and Donohue recommend, the data does not show a positive correlation between abortion rates and crime rates. They are quick to point out that this does not necessarily disprove Levitt's thesis, however, and emphasize that with data this messy and incomplete, it is in all likelihood not even possible to prove or disprove Donohue and Levitt's conclusion.

Q: What kind of impact did legalized abortion have on crime?
A: From a pro-life view of the world: If abortion is murder then we have a million murders a year through abortion.

Q: Did abortion affect the crime rate in any other way?
A: And the few thousand homicides that will be prevented according to our analysis are just nothing--they are a pebble in the ocean relative to the tragedy that is abortion.

Q: Who opposed the abortion movement?
A: unknown

Q: What percentage did crime go up?
A: unknown

Q: What other impact did legalized abortion have on crime?
A: In 2003, Theodore Joyce argued that legalized abortion had little impact on crime,
Did he make any headway in the argument legally or otherwise?
In 2004, the authors published a response, in which they claimed Joyce's argument was flawed due to omitted-variable bias.
In 2004, the authors published a response, in which they claimed Joyce's argument was flawed due to omitted-variable bias.