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Efficiency in Repeated Games Revisited: The Role of Private Strategies

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  • Michihiro Kandori

    (Faculty of Economics, University of Tokyo)

  • Ichiro Obara

    (Department of Economics, UCLA)

Abstract

Most theoretical or applied research on repeated games with imperfect monitoring has restricted attention to public strategies; strategies that only depend on history of publicly observable signals, and perfect public equilibrium (PPE); sequential equilibrium in public strategies. The present paper sheds light on the role of private strategies; strategies that depend on players' own actions in the past as well as observed public signals. Our main finding is that players can sometimes make better use of information by using private strategies and efficiency in repeated games can often be drastically improved. We illustrate this for both games with a small signal space (Anti-folk theorem example) and games with a large signal space, for which the Folk Theorem holds. Our private strategy can be regarded as a machine which consists of two states. We provide two di erent characterizations of our two-state machine equilibrium for general two-person repeated games with imperfect public monitoring.

Suggested Citation

  • Michihiro Kandori & Ichiro Obara, 2003. "Efficiency in Repeated Games Revisited: The Role of Private Strategies," CIRJE F-Series CIRJE-F-255, CIRJE, Faculty of Economics, University of Tokyo.
  • Handle: RePEc:tky:fseres:2003cf255
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    References listed on IDEAS

    as
    1. Obara Ichiro, 2008. "The Full Surplus Extraction Theorem with Hidden Actions," The B.E. Journal of Theoretical Economics, De Gruyter, vol. 8(1), pages 1-28, March.
    2. Ichiro Obara, "undated". "Endogenous Monitoring," UCLA Economics Online Papers 398, UCLA Department of Economics.
    3. Green, Edward J & Porter, Robert H, 1984. "Noncooperative Collusion under Imperfect Price Information," Econometrica, Econometric Society, vol. 52(1), pages 87-100, January.
    4. Michihiro Kandori & Ichiro Obara, 2006. "Less is more: an observability paradox in repeated games," International Journal of Game Theory, Springer;Game Theory Society, vol. 34(4), pages 475-493, November.
    5. Ely, Jeffrey C. & Valimaki, Juuso, 2002. "A Robust Folk Theorem for the Prisoner's Dilemma," Journal of Economic Theory, Elsevier, vol. 102(1), pages 84-105, January.
    6. Mailath, George J. & Morris, Stephen, 2002. "Repeated Games with Almost-Public Monitoring," Journal of Economic Theory, Elsevier, vol. 102(1), pages 189-228, January.
    7. Fudenberg, Drew & Levine, David I & Maskin, Eric, 1994. "The Folk Theorem with Imperfect Public Information," Econometrica, Econometric Society, vol. 62(5), pages 997-1039, September.
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    9. Lehrer, Ehud, 1991. "Internal Correlation in Repeated Games," International Journal of Game Theory, Springer;Game Theory Society, vol. 19(4), pages 431-456.
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    11. Roy Radner & Roger Myerson & Eric Maskin, 1986. "An Example of a Repeated Partnership Game with Discounting and with Uniformly Inefficient Equilibria," Review of Economic Studies, Oxford University Press, vol. 53(1), pages 59-69.
    12. Piccione, Michele, 2002. "The Repeated Prisoner's Dilemma with Imperfect Private Monitoring," Journal of Economic Theory, Elsevier, vol. 102(1), pages 70-83, January.
    13. Mailath George J. & Matthews Steven A. & Sekiguchi Tadashi, 2002. "Private Strategies in Finitely Repeated Games with Imperfect Public Monitoring," The B.E. Journal of Theoretical Economics, De Gruyter, vol. 2(1), pages 1-23, June.
    14. Michihiro Kandori, 1999. "Check Your Partners' Behavior by Randomization: New Efficiency Results on Repeated Games with Imperfect Monitoring," CIRJE F-Series CIRJE-F-45, CIRJE, Faculty of Economics, University of Tokyo.
    15. Ichiro Obara, 2000. "Private Strategy and Efficiency: Repeated Partnership Games Revisited," Econometric Society World Congress 2000 Contributed Papers 1449, Econometric Society.
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