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Gérard Debreu (; 4 July 1921 – 31 December 2004) was a French-born
economist An economist is a professional and practitioner in the social sciences, social science discipline of economics. The individual may also study, develop, and apply theories and concepts from economics and write about economic policy. Within this ...
and
mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change. History On ...
. Best known as a professor of
economics Economics () is the social science that studies the production, distribution, and consumption of goods and services. Economics focuses on the behaviour and interactions of economic agents and how economies work. Microeconomics anal ...
at the
University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant un ...
, where he began work in 1962, he won the 1983
Nobel Memorial Prize in Economic Sciences The Nobel Memorial Prize in Economic Sciences, officially the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel ( sv, Sveriges riksbanks pris i ekonomisk vetenskap till Alfred Nobels minne), is an economics award administered ...
.


Biography

His father was the business partner of his maternal grandfather in lace manufacturing, a traditional industry in Calais. Debreu was orphaned at an early age, as his father committed suicide and his mother died of natural causes. Prior to the start of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
, he received his
baccalauréat The ''baccalauréat'' (; ), often known in France colloquially as the ''bac'', is a French national academic qualification that students can obtain at the completion of their secondary education (at the end of the ''lycée'') by meeting certain ...
and went to
Ambert Ambert (; Auvergnat: ''Embèrt'') is a commune in the Puy-de-Dôme department in Auvergne in central France. Administration Ambert is the seat of the canton of Ambert and the arrondissement of Ambert. It is a sub-prefecture of the department. Th ...
to begin preparing for the entrance examination of a grande école. Later on, he moved from
Ambert Ambert (; Auvergnat: ''Embèrt'') is a commune in the Puy-de-Dôme department in Auvergne in central France. Administration Ambert is the seat of the canton of Ambert and the arrondissement of Ambert. It is a sub-prefecture of the department. Th ...
to Grenoble to complete his preparation, both places being in
Vichy France Vichy France (french: Régime de Vichy; 10 July 1940 – 9 August 1944), officially the French State ('), was the fascist French state headed by Marshal Philippe Pétain during World War II. Officially independent, but with half of its t ...
during World War II. In 1941, he was admitted to the
École Normale Supérieure École may refer to: * an elementary school in the French educational stages normally followed by secondary education establishments (collège and lycée) * École (river), a tributary of the Seine flowing in région Île-de-France * École, S ...
in Paris, along with Marcel Boiteux. He was influenced by Henri Cartan and the Bourbaki writers. When he was about to take the final examinations in 1944, the
Normandy landings The Normandy landings were the landing operations and associated airborne operations on Tuesday, 6 June 1944 of the Allied invasion of Normandy in Operation Overlord during World War II. Codenamed Operation Neptune and often referred to as ...
occurred and he, instead, enlisted in the French army. He was transferred for training to
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and then served in the occupying French forces in Germany until July 1945. Debreu passed the Agrégation de Mathématiques exams at the end of 1945 and the beginning of 1946. By this time, he had become interested in economics, particularly in the general equilibrium theory of
Léon Walras Marie-Esprit-Léon Walras (; 16 December 1834 – 5 January 1910) was a French mathematical economist and Georgist. He formulated the marginal theory of value (independently of William Stanley Jevons and Carl Menger) and pioneered the developme ...
. From 1946 to 1948, he was an assistant in the Centre National de la Recherche Scientifique. During these two and a half years, he made the transition from mathematics to economics. In 1948, Debreu went to the United States on a
Rockefeller Fellowship The Rockefeller Foundation is an American private foundation and philanthropic medical research and arts funding organization based at 420 Fifth Avenue, New York City. The second-oldest major philanthropic institution in America, after the Carneg ...
which allowed him to visit several American universities, as well as those in
Uppsala Uppsala (, or all ending in , ; archaically spelled ''Upsala'') is the county seat of Uppsala County and the fourth-largest city in Sweden, after Stockholm, Gothenburg, and Malmö. It had 177,074 inhabitants in 2019. Located north of the ca ...
and
Oslo Oslo ( , , or ; sma, Oslove) is the capital and most populous city of Norway. It constitutes both a county and a municipality. The municipality of Oslo had a population of in 2022, while the city's greater urban area had a population of ...
in 1949–50. Debreu married Françoise Bled in 1946 and they had two daughters, Chantal and Florence, born in 1946 and 1950 respectively. Debreu died in Paris at the age of 83 of natural causes on
New Year's Eve In the Gregorian calendar, New Year's Eve, also known as Old Year's Day or Saint Sylvester's Day in many countries, is the evening or the entire day of the last day of the year, on 31 December. The last day of the year is commonly referred to ...
, 2004.


Academic career

Debreu began working as a Research Associate and joined the Cowles Commission at the
University of Chicago The University of Chicago (UChicago, Chicago, U of C, or UChi) is a private research university in Chicago, Illinois. Its main campus is located in Chicago's Hyde Park neighborhood. The University of Chicago is consistently ranked among the b ...
in the summer of 1950. He remained there for five years, returning to Paris periodically. In 1954, he published a breakthrough paper, entitled ''Existence of an Equilibrium for a Competitive Economy'', together with
Kenneth Arrow Kenneth Joseph Arrow (23 August 1921 – 21 February 2017) was an American economist, mathematician, writer, and political theorist. He was the joint winner of the Nobel Memorial Prize in Economic Sciences with John Hicks in 1972. In economi ...
, in which they provided a definitive mathematical proof of the existence of a
general equilibrium In economics, general equilibrium theory attempts to explain the behavior of supply, demand, and prices in a whole economy with several or many interacting markets, by seeking to prove that the interaction of demand and supply will result in an o ...
, using topological rather than
calculus Calculus, originally called infinitesimal calculus or "the calculus of infinitesimals", is the mathematics, mathematical study of continuous change, in the same way that geometry is the study of shape, and algebra is the study of generalizati ...
-based methods. In 1955, he moved to
Yale University Yale University is a private research university in New Haven, Connecticut. Established in 1701 as the Collegiate School, it is the third-oldest institution of higher education in the United States and among the most prestigious in the w ...
. In 1959, he published his classical monograph, ''Theory of Value: An Axiomatic Analysis of Economic Equilibrium'' (Cowles Foundation Monographs Series), which is one of the most important works in mathematical economics. He also studied several problems in the theory of
cardinal utility In economics, a cardinal utility function or scale is a utility index that preserves preference orderings uniquely up to positive affine transformations. Two utility indices are related by an affine transformation if for the value u(x_i) of one i ...
, in particular the additive
decomposition Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and ...
of a
utility function As a topic of economics, utility is used to model worth or value. Its usage has evolved significantly over time. The term was introduced initially as a measure of pleasure or happiness as part of the theory of utilitarianism by moral philosoph ...
defined on a
Cartesian product In mathematics, specifically set theory, the Cartesian product of two sets ''A'' and ''B'', denoted ''A''×''B'', is the set of all ordered pairs where ''a'' is in ''A'' and ''b'' is in ''B''. In terms of set-builder notation, that is : A\t ...
of sets. In this monograph, Debreu set up an axiomatic foundation for competitive markets. He also established the existence of an equilibrium using a novel approach. The main idea of his argument is to show that there exists a price system for which the
aggregate Aggregate or aggregates may refer to: Computing and mathematics * collection of objects that are bound together by a root entity, otherwise known as an aggregate root. The aggregate root guarantees the consistency of changes being made within the ...
excess demand correspondence vanishes. He did so by proving a type of fixed-point theorem that is based on the Kakutani fixed-point theorem. In Chapter 7, Debreu introduced the concept of
uncertainty Uncertainty refers to epistemic situations involving imperfect or unknown information. It applies to predictions of future events, to physical measurements that are already made, or to the unknown. Uncertainty arises in partially observable ...
and showed how it could be incorporated into the
deterministic Determinism is a philosophical view, where all events are determined completely by previously existing causes. Deterministic theories throughout the history of philosophy have developed from diverse and sometimes overlapping motives and cons ...
model. Here, he introduced the notion of a contingent
commodity In economics, a commodity is an economic good, usually a resource, that has full or substantial fungibility: that is, the market treats instances of the good as equivalent or nearly so with no regard to who produced them. The price of a co ...
, which is a promise to deliver a good should a certain state of nature be realized. This concept is very frequently used in
financial economics Financial economics, also known as finance, is the branch of economics characterized by a "concentration on monetary activities", in which "money of one type or another is likely to appear on ''both sides'' of a trade". William F. Sharpe"Financia ...
, where it is known as the " Arrow–Debreu security". In 1960–61, he worked at the Center for Advanced Study in the Behavioral Sciences at Stanford and devoted most of his time to the complex proof that appeared in 1962 of a general theorem on the existence of an economic equilibrium. In January 1962, he started working at the
University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant un ...
, where he held the titles of University Professor and Class of 1958 Professor of Economics and Mathematics Emeritus. During his sabbaticals in the late 1960s and 1970s, he visited universities in
Leiden Leiden (; in English and archaic Dutch also Leyden) is a city and municipality in the province of South Holland, Netherlands. The municipality of Leiden has a population of 119,713, but the city forms one densely connected agglomeration w ...
,
Cambridge Cambridge ( ) is a university city and the county town in Cambridgeshire, England. It is located on the River Cam approximately north of London. As of the 2021 United Kingdom census, the population of Cambridge was 145,700. Cambridge bec ...
,
Bonn The federal city of Bonn ( lat, Bonna) is a city on the banks of the Rhine in the German state of North Rhine-Westphalia, with a population of over 300,000. About south-southeast of Cologne, Bonn is in the southernmost part of the Rhine-Ru ...
and
Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. Si ...
. In 1987, he visited the University of Canterbury as an Erskine Fellow, lecturing in economic theory. His later studies centred mainly on the theory of differentiable economies, where he showed that, in general, aggregate
excess demand function In microeconomics, excess demand is a phenomenon where the demand for goods and services exceeds that which the firms can produce. In microeconomics, an excess demand function is a function expressing excess demand for a product—the excess ...
s vanish at a finite number of points – basically, he showed that economies have a finite number of price equilibria. In 1976, he received the French
Legion of Honour The National Order of the Legion of Honour (french: Ordre national de la Légion d'honneur), formerly the Royal Order of the Legion of Honour ('), is the highest French order of merit, both military and civil. Established in 1802 by Napoleo ...
. He was awarded the 1983 Bank of Sweden Prize in Economic Sciences in Memory of Alfred Nobel, for having incorporated new analytical methods into economic theory and for his rigorous reformulation of general equilibrium theory. He was a member of the International Academy of Science, the
American Academy of Arts and Sciences The American Academy of Arts and Sciences (abbreviation: AAA&S) is one of the oldest learned societies in the United States. It was founded in 1780 during the American Revolution by John Adams, John Hancock, James Bowdoin, Andrew Oliver, a ...
, the United States National Academy of Sciences, and the
American Philosophical Society The American Philosophical Society (APS), founded in 1743 in Philadelphia, is a scholarly organization that promotes knowledge in the sciences and humanities through research, professional meetings, publications, library resources, and communit ...
. In 1990, he served as president of the
American Economic Association The American Economic Association (AEA) is a learned society in the field of economics. It publishes several peer-reviewed journals acknowledged in business and academia. There are some 23,000 members. History and Constitution The AEA was esta ...
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Major publications


Books

* * ::''The twenty papers'': The coefficient of resource utilization · A social equilibrium existence theorem · A classical tax-subsidy problem · Existence of an equilibrium for a competitive economy (by ''Gérard Debreu'' and '' Kenneth J. Arrow'') · Valuation equilibrium and Pareto optimum · Representation of a preference ordering by a numerical function · Market equilibrium · Economics under uncertainty · Topological methods in cardinal utility theory · New concepts and techniques for equilibrium analysis · A limit theorem on the core of an economy (by ''Gérard Debreu'' and '' Herbert Scarf'') · Contuinity properties of Paretian utility · Neighboring economic agents · Economies with a finite set of equilibria · Smooth preferences · Excess demand functions · The rate of convergence of the core of an economy · Four aspects of the mathematical theory of economic equilibrium · The application to economics of differential topology and global analysis: differentiable economies · Least concave utility functions *


Book chapters

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Journal articles

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* * (Presidential address delivered at the 103rd meeting of the American Economic Association, 29 December 1990, Washington, DC.

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References


External links

* including the Nobel Lecture December 8, 1983 ''Economic Theory in the Mathematical Mode''
Obituary for Debreu

Guide to the Gérard Debreu Papers
at
The Bancroft Library The Bancroft Library in the center of the campus of the University of California, Berkeley, is the university's primary special-collections library. It was acquired from its founder, Hubert Howe Bancroft, in 1905, with the proviso that it retai ...

Lectures on Mathematical Economics from 1987 at University of Canterbury
via YouTube * * {{DEFAULTSORT:Debreu, Gerard 1921 births 2004 deaths People from Calais French emigrants to the United States French economists Nobel laureates in Economics Mathematical economists Welfare economists General equilibrium theorists French Nobel laureates American Nobel laureates Members of the French Academy of Sciences Members of the United States National Academy of Sciences École Normale Supérieure alumni University of California, Berkeley College of Letters and Science faculty 20th-century American economists Fellows of the Econometric Society Presidents of the Econometric Society Presidents of the American Economic Association Distinguished Fellows of the American Economic Association