American sociologist whose study of the black population of Chicago (1957) demonstrated early in his career the validity of human ecology as an extension of the discipline of sociology.

Duncan received a B.A. from Louisiana State University (1941), an M.A. from the University of Minnesota (1942), and a Ph.D. from the University of Chicago (1949). He served as associate professor of human ecology at the University of Chicago (1957–60), where he had taught since 1951, before becoming a full professor (1960–62). He later taught at the Universities of Michigan (1962–73), Arizona (1973–84), and California in Santa Barbara (1984–87). He introduced many statistical techniques to sociology, such as the statistical causal models typically used in biology. These are examined in great detail in Notes on Social Measurement (1984).

Duncan's widely referenced The American Occupational Structure (1967; with Peter M. Blau) advanced scientific understanding of the structure and development of work-related mobility patterns in the United States. It was the first national intergenerational survey to represent the influences of family background, education, race, region, size of community, and other factors on the occupational mobility of men. The book received the Sorokin Award of the American Sociological Association.