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CK-Equilibria and Informational Efficiency in a Competitive Economy

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  • Gabriel Desgranges

    (Universite de Cergy-Pontoise)

Abstract

We consider a very simple competitive economy with infinitesimal agents and asymmetric information. We define a Common Knowledge (CK hereafter) Equilibrium as a price distribution compatible with CK of market clearing and rationality. At equilibrium, expectational mistakes and incorrect information revelation by price are possible. But, whenever unique, the CK equilibrium is a fully revealing Rational Expectations Equilibrium. Hence uniqueness of equilibrium means market informational efficiency. We give different conditions of uniqueness of equilibrium bearing on the information structure. The first ones emphasize that many informed agents are required for market efficiency. Agents need not be perfectly informed, but each "piece" of information has to be known by a large enough proportion of the population. The main result is a characterization of the information structures allowing for local uniqueness: multiplicity of equilibria obtains when all the agents have to extract information from the price to obtain information about the same event. We show that this result holds in an exchange economy with finitely many goods and generic preferences. Finally, we provide a simple market game in which the CK-equilibria obtain through infinitely repeated elimination of weakly dominated strategies.

Suggested Citation

  • Gabriel Desgranges, 2000. "CK-Equilibria and Informational Efficiency in a Competitive Economy," Econometric Society World Congress 2000 Contributed Papers 1296, Econometric Society.
  • Handle: RePEc:ecm:wc2000:1296
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    References listed on IDEAS

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    Cited by:

    1. Roger Guesnerie & Pedro Jara-Moroni, 2009. "Expectational coordination in simple economic contexts: concepts and analysis with emphasis on strategic substitutabilities," Working Papers halshs-00574957, HAL.
    2. Roger Guesnerie, 2008. "Macroeconomic and monetary policies from the "eductive" viewpoint," Working Papers halshs-00586749, HAL.
    3. Elchanan Ben-Porath, 2007. "Trade with Heterogeneous Beliefs," Levine's Bibliography 122247000000001494, UCLA Department of Economics.
    4. Roger Guesnerie, 2005. "Strategic substitutabilities versus strategic complementarities: Towards a general theory of expectational coordination?," Working Papers halshs-00590856, HAL.
    5. Roger Guesnerie, 2009. "Macroeconomic and Monetary Policies from the Eductive Viewpoint," Central Banking, Analysis, and Economic Policies Book Series,in: Klaus Schmidt-Hebbel & Carl E. Walsh & Norman Loayza (Series Editor) & Klaus Schmidt-Hebbel (Series (ed.), Monetary Policy under Uncertainty and Learning, edition 1, volume 13, chapter 6, pages 171-202 Central Bank of Chile.
    6. Roger Guesnerie & Pedro Jara-Moroni, 2007. "Expectational coordination in a class of economic models: Strategic substitutabilities versus strategic complementarities," Working Papers halshs-00587837, HAL.
    7. Jara-Moroni, Pedro, 2012. "Rationalizability in games with a continuum of players," Games and Economic Behavior, Elsevier, vol. 75(2), pages 668-684.
    8. Roger Guesnerie & Pedro Jara-Moroni, 2011. "Expectational coordination in simple economic contexts," Economic Theory, Springer;Society for the Advancement of Economic Theory (SAET), vol. 47(2), pages 205-246, June.

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