Irving Fisher (February 27, 1867 – April 29, 1947) was an American economist and statistician. He was one of the earliest American neoclassical economists. Joseph Schumpeter described him as “the greatest economist the United States has ever produced”, an assessment later repeated by James Tobin and Milton Friedman.
Fisher made important contributions to utility theory and general equilibrium. He was a pioneer in the rigorous study of intertemporal choice in markets, which led him to develop a theory of capital and interest rates. His research on the quantity theory of money foreshadowed “monetarism”. Fisher was also a pioneer of econometrics, including the development of index numbers.