Gerard Debreu (dəbrōō´), 1921–2005, French-American economist, b. Calais, France. He studied mathematics in France before coming to the United States in 1950, where he worked with the Chicago-based Cowles Foundation for Research in Economics. With such books as Theory of Value (1959), Debreu made mathematical advances in the theory of economic equilibrium, examining how supply and demand are balanced through prices. He taught economics and mathematics at the Univ. of California, Berkeley, from 1962 to 1991, and became an American citizen in 1975. Debreu was awarded the Nobel Memorial Prize in Economic Sciences in 1983.