Fisher, Irving,1867–1947, American economist, b. Saugerties, N.Y., Ph.D. Yale, 1891. He began teaching at Yale in 1890 and was active there until 1935. His earliest work was in mathematics, and he made a distinguished contribution to mathematical economic theory. He was noted chiefly for his studies in managed currency, in which he set forth the theory of the “compensated dollar” whereby purchasing power might be stabilized. His expansion of interest theory included the theory of investment appraisal, which relied on a person's willingness to sacrifice present for future income. He was also one of the first to work out a numbered index system for filing. Fisher's interests were wide; they included activities in academic, business, welfare, and public organizations, especially public health societies. Important among his many books are Mathematical Investigations in the Theory of Value and Prices (1892), Appreciation and Interest (1896), The Nature of Capital and Income (1906), The Rate of Interest (1907), The Making of Index Numbers (1922), and Theory of Interest (1930).
