GERARD DEBREU, a French-born mathematician and economist who taught at Berkeley for three decades, pioneered what later became a widespread deployment of formal, and rigorous, mathematical analysis within economic theory. For his achievements, especially work regarding markets and the general equilibrium, he was awarded the Nobel prize in 1983.
Probably Debreu’s ultimate contribution came in his comparative youth, when he played a leading role in advancing thinking on market- clearing pioneered by Adam Smith, who reasoned that the “invisible hand” would, through price adjustments, allocate goods optimally — an idea extended in the 19th century by Leon Walras.
Smith and Walras contended that all markets — for goods and services, labour, other factors of production — should simultaneously clear, leaving supply and demand in equilibrium.
But whether Walras’s proposed system could be shown to be logically consistent had for decades been unproven. It was Debreu, along with Kenneth Arrow, who finally demonstrated through mathematics the existence of market-clearing equilibrium prices.
Not only did longstanding models now benefit from mathematical proof, but as Debreu reflected, economics as an overall discipline soon witnessed a shift in which “exacting standards of logical rigour became the rule rather than the exception”. The quantity of mathematical formulae in research journals increased to reflect the new standard.
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Developing his major themes regarding general equilibria in papers written and co-written in the early and mid-1950s, Debreu in 1959 published Theory of Value: An Axiomatic Analysis of Economic Equilibrium, a volume soon regarded as a classic. He also made significant progress in general equilibrium theory and consumer theory.
Gerard Debreu was born in Calais in 1921. Enrolling in 1941 to study mathematics at Paris’s Ecole Normale Supérieure, he sheltered for three years from the “dark outside world” of German occupation. In 1944, as the Normandy landings heralded the liberation, he delayed his final exams and enlisted for military service.
He attended officer school in Algeria and served briefly in occupied Germany. But he soon returned to study, looking to convert from mathematics to economics. He joined Paris’s Centre National de la Recherche Scientifique, which, given his altered direction, he recalled displaying “an impressive tolerance for the absence of tangible results”.
Enabled in 1949 by a Rockefeller fellowship to tour US universities, he became a research associate over the next decade for the Cowles Commission for Research in Economics at Chicago and, from 1955, Yale. He received his doctorate in 1956.
Boosted by his early breakthroughs, Debreu worked in 1960 and 1961 in the Center for Advanced Study in the Behavioural Sciences at Stanford, and in 1962 he became Professor of Economics and, from 1975, also of Mathematics, at Berkeley.
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In 1985, after receiving the Nobel prize, he was made a University professor. He retired in 1991 but continued to give lectures and contribute advice to governments.
In academic style Debreu was happier outlining his mathematical proofs and models than engaging in more policy-orientated debates. A man of polished manners, with a fondness for hiking, he on occasion ventured into political fields. He assumed US citizenship after the Watergate crisis, calling his new home “a great country”.
He was made Chevalier of the Légion d’honneur in 1976, and Commander of the French National Order of Merit in 1984.
He married Françoise Bled in 1945; they had two daughters.
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Gerard Debreu, Nobel prize- winning economist, was born on July 4, 1921. He died in Paris on December 31, 2004, aged 83.