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Gerard Debreu (July 4, 1921 – December 31, 2004) is a French economist and mathematician (In July 1975, he became a naturalized citizen of the United States). He won the 1983 Nobel Memorial Prize in Economics.
He was born in Calais. Just prior to the start of World War II he finished college, but instead of preparing for the university he studied at an improvised math curriculum in Ambert. Later on he moved to Grenoble. In 1941 he was admitted to the École Normale Supérieure with Marcel Boiteux, which he was about to graduate from in 1944 when the D-Day made him enlist in the Allies army. He was transferred for training to Algeria and then served in French occupational forces in Germany until July 1945.
Eventually he graduated in the end of 1945 and later became interested in economics, particularly the general equilibrium theory of Leon Walras. He was an assistant in the Centre National de la Recherche Scientifique and then obtained the Rockefeller Fellowship which allowed him to visit several American universities, as well as those in Uppsala and Oslo in 1949-50. Debreu began working as a Research Association at the University of Chicago in the summer of 1950. There he remained for five years, returning to Paris periodically. In 1954 he published a breakthrough paper titled Existence of an Equilibrium for a Competitive Economy (together with Kenneth Arrow). In 1955 he moved to Yale University.
In 1959 he published his classical monograph, Theory of Value: An Axiomatic Analysis of Economic Equilibrium, (Cowles Foundation Monographs Series), which is perhaps the most important work in mathematical economics. In this monograph, Debreu sets up an axiomatic foundation for competitive markets. He establishes the existence of equilibrium using a novel approach. The main idea is to show that there exists a price system for which the aggregate excess demand correspondence vanishes. He does so by proving a fixed point like theorem based on Kakutani's fixed-point theorem. In Chapter 7 of the book Debreu introduces uncertainty and shows how it can be incorporated into the deterministic model. Here he introduces the notion of a contingent commodity, which is a promise to deliver a good should a state of nature realize.
In 1960-61 he worked at Stanford University and since 1962 at the University of California, Berkeley where he held the title University Professor and Class of 1958 Professor of Economics and Mathematics Emeritus. During his leaves in late sixties and seventies he visited universities in Leiden, Cambridge, Bonn, and Paris.
His later studies centred mainly on the theory of differentiable economies where he showed that in general aggregate excess demand functions vanish at a finite number of points. Basically, showing that economies have a finite number of price equilibria.
In 1976 he received the French Legion of Honor. He was awarded the 1983 Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel for his work on general equilibrium economics.
Debreu married Françoise Bled in 1946 and had two daughters, Chantal and Florence, born in 1946 and 1950 respectively.
Debreu died in Paris at the end of 2004 of natural causes.
External links
- The Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel 1983
- Existence of an Equilibrium for a Competitive Economy
- Debreu page at Berkeley
- Obituary for Debreu