Debreu, Gerard, duh BROO, zhay RAHR (1921-2004), a French-born American economist, developed a mathematical model that showed the importance of prices in producing equilibrium (balance) in an economy. Debreu made important contributions to several areas of mathematical economic theory. He devised a general theory of equilibrium and developed some statistical methods that helped to support the theory. For this work, Debreu was awarded the Nobel Prize in economic sciences in 1983.