Gerard Debreu, 83; Economist Won Nobel

Gerard Debreu, a retired UC Berkeley professor who won a Nobel Prize in economics for mathematically proving the classic theory of supply and demand, has died. He was 83.

Debreu died Friday in Paris, his son-in-law, Richard De Soto, told Associated Press. He had suffered a series of strokes and had been in an assisted living center there, De Soto said. “He had been quite ill for the last year,” De Soto said.

The French-born economist and mathematician was a pioneer in the use of mathematics to prove economic theories, UC Berkeley said. His models showed how prices affect the supplies of goods bought and sold -- using numbers to demonstrate the marketplace’s “invisible hand,” first described by landmark 18th century economist-philosopher Adam Smith.

Computer models based on Debreu’s work are routinely used by the World Bank and other agencies for analyzing trends in national economies and world markets.

“He really was the most important contributor to the development of formal math models within economics,” UC Berkeley professor Robert Anderson said in a statement released Wednesday. “He brought to economics a mathematical rigor that had not been seen before.”

That rigor produced lasting changes in economics, making it a more formal and precise science, Anderson said.

Debreu’s work had a “profound and unsurpassed effect on the choice of methods and analytic techniques in economics,” the Royal Swedish Academy of Sciences said in awarding him its 1983 Nobel in economics.

“For very good reasons, mathematics is not understood by the general public,” Debreu told the Christian Science Monitor after winning the award. The machinery and gadgets of everyday life, including automobiles and computers, trace their roots to mathematics, but mathematicians have not done a good job of explaining the connections to laypersons, he said.

“I seek to set up abstract models, couched in mathematical terms, to give an account of the way the many agents of which an economy is composed make decisions and how those decisions are consistent with each other,” Debreu said in describing his approach.

Debreu taught at UC Berkeley for 30 years, joining the institution as it was building up its economics department into an international powerhouse. His award was the first of four Nobels in economics won by UC Berkeley faculty, the school said.

A native of the northern French coastal city of Calais, Debreu interrupted his mathematics studies to enlist in the French Army after the U.S.-led D-day invasion of France in 1944, serving briefly in French occupational forces in Germany until July 1945, UC Berkeley said.

He resumed his studies after the war, shifting his focus to economics, and later became a U.S. citizen. Debreu also held posts at the University of Chicago, Yale University and Stanford University.

Debreu is survived by two daughters, five grandchildren and four great-grandchildren, the university said.

A service is scheduled for Friday in Paris, the school said.