He was hired by Harvard University's Department of Social Relations in 1946, where he received tenure in 1951 and served as acting chair from 1953–1954. He founded the Department of Statistics and served as its first chairman from 1957–1969, 1973, 1975-1977. He chaired the Department of Biostatistics at the Harvard School of Public Health in 1977-1981 and later the Department of Health Policy and Management in the 1980s. His four chairmanships have not been matched. He also taught courses at Harvard Law School and Harvard's Kennedy School of Government.