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Correcting the concentration index: A comment


  • Wagstaff, Adam


In a recent article in this journal, Erreygers [Erreygers, G., 2008. Correcting the concentration index. Journal of Health Economics] has proposed a new measure of income-related health inequality to overcome three shortcomings of the concentration index (CI). I think Erreygers is absolutely right to probe on these issues, and I welcome his generalization of my normalization which was specific to the case of a binary health indicator. However, I have misgivings about his paper. His goal of correcting the CI so as to make it usable with interval-scale variables seems misguided. The CI reflects a commitment on the part of the analyst to measuring relative inequality. Armed only with an interval-scale variable, one simply has to accept that one can meaningfully measure only differences and therefore settle for measuring absolute inequality. Erreygers, index inevitably ends up as a measure of absolute inequality. His objection to my approach to getting round the bounds problem is that my normalization of the CI does not produce a measure of absolute inequality. But that was never my intention! In this comment I also show that - somewhat paradoxically at first glance - my index is also not a pure index of relative inequality. This seems to be an inevitable consequence of tackling the bounds issue.

Suggested Citation

  • Wagstaff, Adam, 2009. "Correcting the concentration index: A comment," Journal of Health Economics, Elsevier, vol. 28(2), pages 516-520, March.
  • Handle: RePEc:eee:jhecon:v:28:y:2009:i:2:p:516-520

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    References listed on IDEAS

    1. Wagstaff, Adam & Paci, Pierella & van Doorslaer, Eddy, 1991. "On the measurement of inequalities in health," Social Science & Medicine, Elsevier, vol. 33(5), pages 545-557, January.
    2. ERREYGERS, Guido, 2006. "Beyond the Health Concentration Index: An Atkinson alternative for the measurement of the socioeconomic inequality of health," Working Papers 2006029, University of Antwerp, Faculty of Applied Economics.
    3. Wagstaff, Adam & van Doorslaer, Eddy & Watanabe, Naoko, 2003. "On decomposing the causes of health sector inequalities with an application to malnutrition inequalities in Vietnam," Journal of Econometrics, Elsevier, vol. 112(1), pages 207-223, January.
    4. Clarke, Philip M. & Gerdtham, Ulf-G. & Johannesson, Magnus & Bingefors, Kerstin & Smith, Len, 2002. "On the measurement of relative and absolute income-related health inequality," Social Science & Medicine, Elsevier, vol. 55(11), pages 1923-1928, December.
    5. Wagstaff, Adam, 2002. "Inequality aversion, health inequalities and health achievement," Journal of Health Economics, Elsevier, vol. 21(4), pages 627-641, July.
    6. Gastwirth, Joseph L, 1972. "The Estimation of the Lorenz Curve and Gini Index," The Review of Economics and Statistics, MIT Press, vol. 54(3), pages 306-316, August.
    7. Adam Wagstaff, 2005. "The bounds of the concentration index when the variable of interest is binary, with an application to immunization inequality," Health Economics, John Wiley & Sons, Ltd., vol. 14(4), pages 429-432.
    8. Zheng, Buhong, 1994. "Can a Poverty Index Be Both Relative and Absolute?," Econometrica, Econometric Society, vol. 62(6), pages 1453-1458, November.
    9. Wagstaff, Adam & Watanabe, Naoko, 2000. "Socioeconomic inequalities in child malnutrition in the developing world," Policy Research Working Paper Series 2434, The World Bank.
    10. Bleichrodt, Han & van Doorslaer, Eddy, 2006. "A welfare economics foundation for health inequality measurement," Journal of Health Economics, Elsevier, vol. 25(5), pages 945-957, September.
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