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The Two Margin Problem in Insurance Markets

Author

Listed:
  • Michael Geruso
  • Timothy J. Layton
  • Grace McCormack
  • Mark Shepard

Abstract

Insurance markets often feature consumer sorting along both an extensive margin (whether to buy) and an intensive margin (which plan to buy). We present a new graphical theoretical framework that extends the workhorse model to incorporate both selection margins simultaneously. A key insight from our framework is that policies aimed at addressing one margin of selection often involve an economically meaningful trade-off on the other margin in terms of prices, enrollment, and welfare. For example, while a larger penalty for opting to remain uninsured reduces the uninsurance rate, it also tends to lead to unraveling of generous coverage because the newly insured are healthier and sort into less generous plans, driving down the relative prices of those plans. While risk adjustment transfers shift enrollment from lower- to higher-generosity plans, they also sometimes increase the uninsurance rate by raising the prices of less generous plans, which are the entry points into the market. We illustrate these trade-offs in an empirical sufficient statistics approach that is tightly linked to the graphical framework. Using data from Massachusetts, we show that in many policy environments these trade-offs can be empirically meaningful and can cause these policies to have unexpected consequences for overall social welfare.

Suggested Citation

  • Michael Geruso & Timothy J. Layton & Grace McCormack & Mark Shepard, 2019. "The Two Margin Problem in Insurance Markets," NBER Working Papers 26288, National Bureau of Economic Research, Inc.
  • Handle: RePEc:nbr:nberwo:26288
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    References listed on IDEAS

    as
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    1. Richard Domurat & Isaac Menashe & Wesley Yin, 2019. "The Role of Behavioral Frictions in Health Insurance Marketplace Enrollment and Risk: Evidence from a Field Experiment," NBER Working Papers 26153, 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
    • G22 - Financial Economics - - Financial Institutions and Services - - - Insurance; Insurance Companies; Actuarial Studies
    • H51 - Public Economics - - National Government Expenditures and Related Policies - - - Government Expenditures and Health
    • I1 - Health, Education, and Welfare - - Health
    • I13 - Health, Education, and Welfare - - Health - - - Health Insurance, Public and Private

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