La théorie du déséquilibre

IV) La théorie du déséquilibre

 Cette théorie, apparue au début des années 70, notamment sous l'impulsion de J.P.Benassy, J.Drèze et E.Malinvaud, se propose de donner certains fondements micro-économiques à certaines des thèses de Keynes.

Autres auteurs américains

Axel Leijonhufvud is a so-called “Post-Walrasian” (or disequilibrium Keynesian/coordination Keynesian), and – like Post Keynesians – he is critical of neoclassical synthesis Keynesianism based on neo-Walrasian theory.

The leading economists in the Post-Walrasian movement are Don Patinkin (1922–1995) and Robert W. Clower (1926–2011), as well as Axel Leijonhufvud.

Leijonhufvud presented a bold new interpretation of Keynes’s General Theory and a critique of the neoclassical synthesis in

On Keynesian Economics and the Economics of Keynes: A Study in Monetary Theory (New York and London, 1968).

Both Clower and Leijonhufvud seem to share these common ideas:

(1) they criticise neo-Walrasian theory, and in particular the supposed market clearing mechanisms summed up in the metaphor of the “Walrasian auctioneer” who clears all markets;

(2) a dynamic disequilibrium approach to economics and interpretation of Keynes’s theory;

(3) the recognition that incomplete information of economic agents prevents market clearing mechanisms;

(4) we have an economic world of slow price adjustments and sometimes false price signals: the Walrasian assumption of instantaneously or near instantaneously adjusting prices is a myth, and once it is rejected we see there is no guarantee at all that decentralised market systems will coordinate economic activity to create full employment, and

(5) the idea that what is needed today is a reconstructed “Post Walrasian macroeconomics” which is derived from Marshallian microfoundations, not Walrasian microfoundations.

Leijonhufvud rejects interpretations based on wage rigidity, and he rejects explanations of depression that depend on monopolies, labor unions, and the like. These interpretations of involuntary unemployment imply that “if ‘competition’ could only be restored, ‘automatic forces’ would take care of the employment problem” ...

Leijonhufvud notes that Keynes was critical of such explanations.

Dans "Macro-économie et théorie du déséquilibre", en 1984, J.P.Benassy, quoique appartenant à l'école néo-classique, admet qu'il peut exister des échanges à des prix qui ne sont pas "d'équilibre concurrentiel", et de plus, qu'on peut envisager un chômage involontaire prolongé, d'où le nom de déséquilibre. On suppose que des échanges peuvent avoir lieu dans ces conditions.

Dans ce cas de figure, il n'y a pas d'égalité entre offres et demandes, et Benassy énonce des règles de rationnement qui s'appliquent aux agents. Certains acteurs de l'économie se trouvent alors en position de manque quantitatif car ils subissent des règles de rationnement.

Dans le cas du chomâge

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