Passage: Born to a Jewish family in Pottsville, Pennsylvania, Becker earned a B.A. at Princeton University in 1951, and a Ph.D. at the University of Chicago in 1955 with a thesis entitled The Economics of Racial Discrimination. At Chicago, Becker was influenced by Milton Friedman, whom Becker called "by far the greatest living teacher I have ever had". Before turning 30, he began to teach at Columbia University in 1957, and in 1970 returned to the University of Chicago. In 1965 he was elected as a Fellow of the American Statistical Association. Becker was a founding partner of TGG Group, a business and philanthropy consulting company. Becker won the John Bates Clark Medal in 1967. He was elected a Fellow of the American Academy of Arts and Sciences in 1972, and was a member (and for a time the President) of the Mont Pelerin Society. Becker also received the National Medal of Science in 2000.A political conservative, he wrote a monthly column for Business Week from  1985 to 2004, alternating with liberal Princeton economist Alan Blinder. In 1996 Becker was a senior adviser to Republican Presidential Candidate Robert Dole. In December 2004, Becker started a joint weblog with Judge Richard Posner entitled The Becker-Posner Blog."The Becker-Posner Blog". uchicagolaw. University of Chicago Law School.Becker's first wife was Doria Slote, from 1954 until her death in 1970. The marriage produced two daughters, Catherine Becker and Judy Becker. About ten years later, in 1980 Becker married Guity Nashat, a historian of the Middle East whose research interests overlapped his own. Becker had two stepsons, Cyrus Claffey and Michael Claffey, from his second marriage.Becker died in Chicago, Illinois, aged 83, on May 3, 2014, after complications from surgery at Northwestern Memorial Hospital.In 2014 he was honored in a three-day conference organized at the University of Chicago.

Question: What research did Becker work on for his doctorate?
The Economics of Racial Discrimination