Steven Levitt, PhD '94, a professor at the University of Chicago, broadened the role of economics with his studies of topics such as criminal behavior, collusion in professional sports, and the impact of economic issues in politics. Freakonomics: A Rogue Economist Explores the Hidden Side of Everything, which he coauthored with journalist Stephen ­Dubner, has been on best-seller lists for two years. The book proposes that knowing what to measure and how to measure it is central to understanding contemporary life. Levitt has been named the most influential young U.S. economist and is among Time's "100 People Who Shape Our World." At a talk hosted by the Undergraduate Economics Association last year, Levitt described his work on the role of altruism in economic interactions and on the economics of gangs.