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Adverse Selection, Moral Hazard and the Demand for Medigap Insurance

Author

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  • Michael P. Keane

    (Nuffield College, University of Oxford)

  • Olena Stavrunova

    (University of Technology, Sydney, Australia)

Abstract

The size of adverse selection and moral hazard e ects in health insurance markets has important policy implications. For example, if adverse selection e ects are small while moral hazard e ects are large, conventional remedies for ineciencies created by adverse selection (e.g., mandatory insurance enrolment) may lead to substantial increases in health care spending. Unfortunately, there is no consensus on the magnitudes of adverse selection vs. moral hazard. This paper sheds new light on this important topic by studying the US Medigap (supplemental) health insurance market. While both adverse selection and moral hazard e ects of Medigap have been studied separately, this is the rst paper to estimate both in an uni ed econometric framework. We develop an econometric model of insurance demand and health care expenditure, where adverse selection is measured by sensitivity of insurance demand to expected expenditure. The model allows for correlation between unobserved determinants of expenditure and insurance demand, and for heterogeneity in the size of moral hazard e ects. Inference relies on an MCMC algorithm with data augmentation. Our results suggest there is adverse selection into Medigap, but the e ect is small. A one standard deviation increase in expenditure risk raises the probability of insurance purchase by 0.037. In contrast, our estimate of the moral hazard e ect is much larger. On average, Medigap coverage increases health care expenditure by 32%.

Suggested Citation

  • Michael P. Keane & Olena Stavrunova, 2012. "Adverse Selection, Moral Hazard and the Demand for Medigap Insurance," Economics Papers 2012-W10, Economics Group, Nuffield College, University of Oxford.
  • Handle: RePEc:nuf:econwp:1210
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    1. Gilleskie, Donna B. & Mroz, Thomas A., 2004. "A flexible approach for estimating the effects of covariates on health expenditures," Journal of Health Economics, Elsevier, vol. 23(2), pages 391-418, March.
    2. Chiappori, Pierre-Andre & Durand, Franck & Geoffard, Pierre-Yves, 1998. "Moral hazard and the demand for physician services: First lessons from a French natural experiment," European Economic Review, Elsevier, vol. 42(3-5), pages 499-511, May.
    3. John Geweke, 2004. "Getting It Right: Joint Distribution Tests of Posterior Simulators," Journal of the American Statistical Association, American Statistical Association, vol. 99, pages 799-804, January.
    4. Manning, Willard G, et al, 1987. "Health Insurance and the Demand for Medical Care: Evidence from a Randomized Experiment," American Economic Review, American Economic Association, vol. 77(3), pages 251-277, June.
    5. Mullahy, John, 1998. "Much ado about two: reconsidering retransformation and the two-part model in health econometrics," Journal of Health Economics, Elsevier, vol. 17(3), pages 247-281, June.
    6. John Mullahy, 1998. "Much Ado About Two: Reconsidering Retransformation and the Two-Part Model in Health Economics," NBER Technical Working Papers 0228, National Bureau of Economic Research, Inc.
    7. Kimball, Miles S & Sahm, Claudia R & Shapiro, Matthew D, 2008. "Imputing Risk Tolerance From Survey Responses," Journal of the American Statistical Association, American Statistical Association, vol. 103(483), pages 1028-1038.
    8. Rubin, Donald B, 1986. "Statistical Matching Using File Concatenation with Adjusted Weights and Multiple Imputations," Journal of Business & Economic Statistics, American Statistical Association, vol. 4(1), pages 87-94, January.
    9. de Meza, David & Webb, David C, 2001. "Advantageous Selection in Insurance Markets," RAND Journal of Economics, The RAND Corporation, vol. 32(2), pages 249-262, Summer.
    10. Deb, Partha & Munkin, Murat K. & Trivedi, Pravin K., 2006. "Private Insurance, Selection, and Health Care Use: A Bayesian Analysis of a Roy-Type Model," Journal of Business & Economic Statistics, American Statistical Association, vol. 24, pages 403-415, October.
    11. Munkin, Murat K. & Trivedi, Pravin K., 2008. "Bayesian analysis of the ordered probit model with endogenous selection," Journal of Econometrics, Elsevier, vol. 143(2), pages 334-348, April.
    12. Manning, Willard G. & Basu, Anirban & Mullahy, John, 2005. "Generalized modeling approaches to risk adjustment of skewed outcomes data," Journal of Health Economics, Elsevier, vol. 24(3), pages 465-488, May.
    13. Michael Keane & Olena Stavrunova, 2011. "A smooth mixture of Tobits model for healthcare expenditure," Health Economics, John Wiley & Sons, Ltd., vol. 20(9), pages 1126-1153, September.
    14. Hanming Fang & Michael P. Keane & Dan Silverman, 2008. "Sources of Advantageous Selection: Evidence from the Medigap Insurance Market," Journal of Political Economy, University of Chicago Press, vol. 116(2), pages 303-350, April.
    15. Fruhwirth-Schnatter S., 2001. "Markov Chain Monte Carlo Estimation of Classical and Dynamic Switching and Mixture Models," Journal of the American Statistical Association, American Statistical Association, vol. 96, pages 194-209, March.
    16. Dardanoni, Valentino & Li Donni, Paolo, 2012. "Incentive and selection effects of Medigap insurance on inpatient care," Journal of Health Economics, Elsevier, vol. 31(3), pages 457-470.
    17. Geweke, John & Keane, Michael, 2007. "Smoothly mixing regressions," Journal of Econometrics, Elsevier, vol. 138(1), pages 252-290, May.
    18. Hurd, Michael D. & McGarry, Kathleen, 1997. "Medical insurance and the use of health care services by the elderly," Journal of Health Economics, Elsevier, vol. 16(2), pages 129-154, April.
    19. Patrick Bajari & Christina Dalton & Han Hong & Ahmed Khwaja, 2014. "Moral hazard, adverse selection, and health expenditures: A semiparametric analysis," RAND Journal of Economics, RAND Corporation, vol. 45(4), pages 747-763, December.
    20. Pierre-Andre Chiappori & Bernard Salanie, 2000. "Testing for Asymmetric Information in Insurance Markets," Journal of Political Economy, University of Chicago Press, vol. 108(1), pages 56-78, February.
    21. Harris, Katherine M. & Keane, Michael P., 1998. "A model of health plan choice:: Inferring preferences and perceptions from a combination of revealed preference and attitudinal data," Journal of Econometrics, Elsevier, vol. 89(1-2), pages 131-157, November.
    22. Alma Cohen & Peter Siegelman, 2010. "Testing for Adverse Selection in Insurance Markets," Journal of Risk & Insurance, The American Risk and Insurance Association, vol. 77(1), pages 39-84, March.
    23. Buntin, Melinda Beeuwkes & Zaslavsky, Alan M., 2004. "Too much ado about two-part models and transformation?: Comparing methods of modeling Medicare expenditures," Journal of Health Economics, Elsevier, vol. 23(3), pages 525-542, May.
    24. Cardon, James H & Hendel, Igal, 2001. "Asymmetric Information in Health Insurance: Evidence from the National Medical Expenditure Survey," RAND Journal of Economics, The RAND Corporation, vol. 32(3), pages 408-427, Autumn.
    25. Geweke, John, 2007. "Interpretation and inference in mixture models: Simple MCMC works," Computational Statistics & Data Analysis, Elsevier, vol. 51(7), pages 3529-3550, April.
    26. Wolfe, John R. & Goddeeris, John H., 1991. "Adverse selection, moral hazard, and wealth effects in the medigap insurance market," Journal of Health Economics, Elsevier, vol. 10(4), pages 433-459.
    27. John Geweke, 1991. "Evaluating the accuracy of sampling-based approaches to the calculation of posterior moments," Staff Report 148, Federal Reserve Bank of Minneapolis.
    28. Michael Rothschild & Joseph Stiglitz, 1976. "Equilibrium in Competitive Insurance Markets: An Essay on the Economics of Imperfect Information," The Quarterly Journal of Economics, President and Fellows of Harvard College, vol. 90(4), pages 629-649.
    29. Munkin M & Trivedi P. K, 2009. "Incentives and Selection Effects of Drug Coverage on Total Drug Expenditure: a Finite Mixture Approach," Health, Econometrics and Data Group (HEDG) Working Papers 09/22, HEDG, c/o Department of Economics, University of York.
    30. Manning, Willard G., 1998. "The logged dependent variable, heteroscedasticity, and the retransformation problem," Journal of Health Economics, Elsevier, vol. 17(3), pages 283-295, June.
    31. Hanming Fang & Lauren Nicholas & Daniel Silverman, 2010. "Cognitive Ability and Retiree Health Care Expenditure," Working Papers wp230, University of Michigan, Michigan Retirement Research Center.
    32. Partha Deb & Murat K. Munkin & Pravin K. Trivedi, 2006. "Bayesian analysis of the two‐part model with endogeneity: application to health care expenditure," Journal of Applied Econometrics, John Wiley & Sons, Ltd., vol. 21(7), pages 1081-1099, November.
    33. Buchmueller, Thomas, 2006. "Price and the health plan choices of retirees," Journal of Health Economics, Elsevier, vol. 25(1), pages 81-101, January.
    34. Ahmed W. Khwaja, 2001. "Health Insurance, Habits and Health Outcomes: A Dynamic Stochastic Model of Investment in Health," Computing in Economics and Finance 2001 166, Society for Computational Economics.
    35. Tomas Philipson & John Cawley, 1999. "An Empirical Examination of Information Barriers to Trade in Insurance," American Economic Review, American Economic Association, vol. 89(4), pages 827-846, September.
    36. Alma Cohen, 2005. "Asymmetric Information and Learning: Evidence from the Automobile Insurance Market," The Review of Economics and Statistics, MIT Press, vol. 87(2), pages 197-207, May.
    37. Murat K. Munkin & Pravin K. Trivedi, 2010. "Disentangling incentives effects of insurance coverage from adverse selection in the case of drug expenditure: a finite mixture approach," Health Economics, John Wiley & Sons, Ltd., vol. 19(9), pages 1093-1108, September.
    38. Ettner, Susan L., 1997. "Adverse selection and the purchase of Medigap insurance by the elderly," Journal of Health Economics, Elsevier, vol. 16(5), pages 543-562, October.
    39. Blough, David K. & Madden, Carolyn W. & Hornbrook, Mark C., 1999. "Modeling risk using generalized linear models," Journal of Health Economics, Elsevier, vol. 18(2), pages 153-171, April.
    40. Amy Finkelstein & Kathleen McGarry, 2006. "Multiple Dimensions of Private Information: Evidence from the Long-Term Care Insurance Market," American Economic Review, American Economic Association, vol. 96(4), pages 938-958, September.
    41. Manning, Willard G. & Mullahy, John, 2001. "Estimating log models: to transform or not to transform?," Journal of Health Economics, Elsevier, vol. 20(4), pages 461-494, July.
    42. Gruber, Jonathan & Washington, Ebonya, 2005. "Subsidies to employee health insurance premiums and the health insurance market," Journal of Health Economics, Elsevier, vol. 24(2), pages 253-276, March.
    43. Chib, Siddhartha, 1992. "Bayes inference in the Tobit censored regression model," Journal of Econometrics, Elsevier, vol. 51(1-2), pages 79-99.
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    More about this item

    Keywords

    Health insurance; adverse selection; moral hazard; health care expenditure;
    All these keywords.

    JEL classification:

    • I13 - Health, Education, and Welfare - - Health - - - Health Insurance, Public and Private
    • D82 - Microeconomics - - Information, Knowledge, and Uncertainty - - - Asymmetric and Private Information; Mechanism Design
    • C34 - Mathematical and Quantitative Methods - - Multiple or Simultaneous Equation Models; Multiple Variables - - - Truncated and Censored Models; Switching Regression Models
    • C35 - Mathematical and Quantitative Methods - - Multiple or Simultaneous Equation Models; Multiple Variables - - - Discrete Regression and Qualitative Choice Models; Discrete Regressors; Proportions

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