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Insisting on a Non-Negative Price: Oligopoly, Uncertainty, Welfare, and Multiple Equilibria

  • Johan Lagerlöf

I study Cournot competition under incomplete information about demand while assuming that market price must be non-negative for all demand realizations. Although this assumption is very natural, it has only rarely been made in the earlier literature. Yet it has important economic consequences: (1) multiple (symmetric, pure strategy) equilibria can exist, despite the fact that demand and cost are linear; and (2) expected total surplus can be larger when the firms do not know demand than when they do, a result which has important implications for the social desirability of information sharing. The arguments of the paper are relevant also for price competition and for uncertainty about, e.g., cost or the number of firms, and these issues are discussed. ZUSAMMENFASSUNG - (Bestehen auf einen nichtnegativen Preis: Oligopol, Ungewißheit, Wohlfahrt und multiple Gleichgewichte) In diesem Beitrag wird Cournot-Wettbewerb bei unvollständiger Information über die Nachfrage untersucht und unterstellt, daß der Marktpreis für alle Realisierungen der Nachfrage nichtnegativ ist. Obgleich diese Annahme sehr selbstverständlich ist, ist sie nur selten in der früheren Literatur verwendet worden. Dennoch hat sie wichtige ökonomische Konsequenzen: (1) können multiple Gleichgewichte existieren (symmetrisch, bei reinen Strategien), obwohl Nachfrage und Kosten linear sind; und (2) kann erwarteter Gesamtüberschuß größer sein, wenn die Unternehmen die Nachfrage nicht kennen als im Falle sie ihnen nicht bekannt ist. Dieses Ergebnis hat wichtige Implikationen für die soziale Erwünschtheit der gemeinsamen Nutung von Information ("Information sharing"). Die Argumente des Beitrags sind auch für Preiskonkurrenz und für Ungewißheit beispielsweise hinsichtlich der Kosten oder der Zahl von Unternehmen relevant. Sie werden abschließend besprochen.

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Paper provided by Wissenschaftszentrum Berlin (WZB), Research Unit: Competition and Innovation (CIG) in its series CIG Working Papers with number SP II 2003-04.

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Length: 26 pages
Date of creation: Jun 2003
Date of revision:
Handle: RePEc:wzb:wzebiv:spii2003-04
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  1. Amir, Rabah, 1996. "Cournot Oligopoly and the Theory of Supermodular Games," Games and Economic Behavior, Elsevier, vol. 15(2), pages 132-148, August.
  2. Li, Lode., 1985. "Cournot Oligopoly with Information Sharing," Working Papers 561, California Institute of Technology, Division of the Humanities and Social Sciences.
  3. Rabah Amir & Val E. Lambson, 1998. "On the Effects of Entry in Cournot Markets," CIE Discussion Papers 1998-06, University of Copenhagen. Department of Economics. Centre for Industrial Economics.
  4. Malueg, David A & Tsutsui, Shunichi O, 1998. "Oligopoly Information Exchange When Non-negative Price and Output Constraints May Bind," Australian Economic Papers, Wiley Blackwell, vol. 37(4), pages 363-71, December.
  5. Raith, Michael, 1996. "A General Model of Information Sharing in Oligopoly," Journal of Economic Theory, Elsevier, vol. 71(1), pages 260-288, October.
  6. Basar, Tamer & Ho, Yu-Chi, 1974. "Informational properties of the Nash solutions of two stochastic nonzero-sum games," Journal of Economic Theory, Elsevier, vol. 7(4), pages 370-387, April.
  7. Xavier Vives, 1990. "Trade Association Disclosure Rules, Incentives to Share Information, and Welfare," RAND Journal of Economics, The RAND Corporation, vol. 21(3), pages 409-430, Autumn.
  8. Xavier Vives, 2001. "Oligopoly Pricing: Old Ideas and New Tools," MIT Press Books, The MIT Press, edition 1, volume 1, number 026272040x, June.
  9. Jean-Pierre Ponssard, 1979. "The Strategic Role of Information on the Demand Function in an Oligopolistic Market," Management Science, INFORMS, vol. 25(3), pages 243-250, March.
  10. Novshek, William, 1985. "On the Existence of Cournot Equilibrium," Review of Economic Studies, Wiley Blackwell, vol. 52(1), pages 85-98, January.
  11. Kai-Uwe Kühn, 2001. "Fighting collusion by regulating communication between firms," Economic Policy, CEPR;CES;MSH, vol. 16(32), pages 167-204, 04.
  12. Vives, Xavier, 1984. "Duopoly information equilibrium: Cournot and bertrand," Journal of Economic Theory, Elsevier, vol. 34(1), pages 71-94, October.
  13. Malueg, David A. & Tsutsui, Shunichi O., 1996. "Duopoly information exchange: The case of unknown slope," International Journal of Industrial Organization, Elsevier, vol. 14(1), pages 119-136.
  14. Gal-Or, Esther, 1986. "Information Transmission-Cournot and Bertrand Equilibria," Review of Economic Studies, Wiley Blackwell, vol. 53(1), pages 85-92, January.
  15. William Novshek & Hugo Sonnenschein, 1982. "Fulfilled Expectations Cournot Duopoly with Information Acquisition and Release," Bell Journal of Economics, The RAND Corporation, vol. 13(1), pages 214-218, Spring.
  16. Weitzman, Martin L, 1974. "Prices vs. Quantities," Review of Economic Studies, Wiley Blackwell, vol. 41(4), pages 477-91, October.
  17. Gal-Or, Esther, 1985. "Information Sharing in Oligopoly," Econometrica, Econometric Society, vol. 53(2), pages 329-43, March.
  18. Richard N. Clarke, 1983. "Collusion and the Incentives for Information Sharing," Bell Journal of Economics, The RAND Corporation, vol. 14(2), pages 383-394, Autumn.
  19. Malueg, David A. & Tsutsui, Shunichi O., 1998. "Distributional assumptions in the theory of oligopoly information exchange1," International Journal of Industrial Organization, Elsevier, vol. 16(6), pages 785-797, November.
  20. Shapiro, Carl, 1986. "Exchange of Cost Information in Oligopoly," Review of Economic Studies, Wiley Blackwell, vol. 53(3), pages 433-46, July.
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