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Equilibrium in a Competitive Insurance Market Under Adverse Selection with Endogenous Information

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  • Joseph E. Stiglitz
  • Jungyoll Yun
  • Andrew Kosenko

Abstract

This paper investigates the existence and nature of equilibrium in a competitive insurance market under adverse selection with endogenously determined information structures. Rothschild-Stiglitz (RS) characterized the self-selection equilibrium under the assumption of exclusivity, enforcement of which required full information about contracts purchased. By contrast, the Akerlof price equilibrium described a situation where the insurance firm has no information about sales to a particular individual. We show that with more plausible information assumptions - no insurance firm has full information but at least knows how much he has sold to any particular individual - neither the RS quantity constrained equilibrium nor the Akerlof price equilibrium are sustainable. But when the information structure itself is endogenous - firms and consumers decide what information about insurance purchases to reveal to whom - there always exists a Nash equilibrium. Strategies for firms consist of insurance contracts to offer and information-revelation strategies; for customers - buying as well as information revelation strategies. The equilibrium set of insurance contracts is unique: the low risk individual obtains insurance corresponding to the pooling contract most preferred by him; the high risk individual, that plus (undisclosed) supplemental insurance at his own actuarial odds resulting in his being fully insured. Equilibrium information revelation strategies of firms entail some but not complete information sharing. However, in equilibrium all individuals are induced to tell the truth. The paper shows how the analysis extends to cases where there are more than two groups of individuals and where firms can offer multiple insurance contracts.

Suggested Citation

  • Joseph E. Stiglitz & Jungyoll Yun & Andrew Kosenko, 2017. "Equilibrium in a Competitive Insurance Market Under Adverse Selection with Endogenous Information," NBER Working Papers 23556, National Bureau of Economic Research, Inc.
  • Handle: RePEc:nbr:nberwo:23556
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    References listed on IDEAS

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    Citations

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    Cited by:

    1. Pradeep Dubey & John Geanakoplos, 2018. "Non-Exclusive Insurance with Free Entry: A Pedagogical Note," Department of Economics Working Papers 18-05, Stony Brook University, Department of Economics.
    2. Jing Jian Xiao & Chunsheng Tao, 2020. "Consumer finance/household finance: the definition and scope," China Finance Review International, Emerald Group Publishing Limited, vol. 11(1), pages 1-25, June.
    3. Pradeep Dubey & John Geanakoplos, 2014. "Games with Money and Status: How Best to Incentivize Work," Cowles Foundation Discussion Papers 1954, Cowles Foundation for Research in Economics, Yale University.
    4. Kosenko, Andrew & Stiglitz, Joseph & Yun, Jungyoll, 2023. "Bilateral information disclosure in adverse selection markets with nonexclusive competition," Journal of Economic Behavior & Organization, Elsevier, vol. 205(C), pages 144-168.
    5. Chen, Bingzheng & Feng, Frank Y. & Powers, Michael R. & Qiu, Joseph, 2019. "Risk-revealing contracts for government-sponsored microinsurance," Pacific-Basin Finance Journal, Elsevier, vol. 57(C).
    6. Joseph E. Stiglitz, 2017. "The Revolution of Information Economics: The Past and the Future," NBER Working Papers 23780, National Bureau of Economic Research, Inc.

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    More about this item

    JEL classification:

    • D82 - Microeconomics - - Information, Knowledge, and Uncertainty - - - Asymmetric and Private Information; Mechanism Design
    • D86 - Microeconomics - - Information, Knowledge, and Uncertainty - - - Economics of Contract Law

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