James Heckman
James Heckman is an economist at the University of Chicago. He was the winner of The Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel in 2000 for his pioneering work in econometrics and microeconomics.
Heckman began his career as a graduate student at the University of Chicago. However, he was unable to pass the core exams, and left with a Masters degree after his first year. Heckman then received his Ph.D. in economics from Princeton University in 1971, and served as an Assistant Professor at Columbia University before returning to the University of Chicago.
Heckman is most famous for introducing the concept of "selection bias" into modern econometrics. The literature has always been complex, but the main idea is fairly simple. Economists routinely take data on wages to calculate average wages. Many subjects are unemployed, and thus would have missing wages. Before Heckman, economists would simply discard all records with missing wages and then calculate averages using the remaining observations. Heckman shows that this process can lead to selection bias because observations do not have missing wages at random. For instance, poorer individuals of one group may be unemployed more often, so average wages may be too high for this group. Thus, Heckman's work has persuaded economists to treat missing observations more carefully.