From 1922-29, he directed the fellowship program of the Laura Spelman Rockefeller Memorial Fund, focusing on support for quantitative social and behavioral science. He was an advisor to President Herbert Hoover, especially on farm issues. In 1931, he became dean of the Division of Social Sciences at the University of Chicago—a center for quantitative research. He was not popular with the faculty and in 1934 Ruml became an executive of Macy's, parent company of the department store, rising to chairman in 1945. He also served as a director of the New York Federal Reserve Bank (1937–1947), and was its chairman from 1941 until 1946; he was active at the Bretton Woods Conference (1944) that established the international monetary system. Ruml was active in New Deal planning agencies, but his plans never saw fruition.