Conindex: Estimation of Concentration Indices

Overview

Journal Stata J

Date 2016 Apr 8

PMID 27053927

Citations 193

Authors

Owen ODonnell

Stephen ONeill

Tom Van Ourti

Brendan Walsh

Affiliations

Soon will be listed here.

Abstract

Concentration indices are frequently used to measure inequality in one variable over the distribution of another. Most commonly, they are applied to the measurement of socioeconomic-related inequality in health. We introduce a user-written Stata command which provides point estimates and standard errors of a range of concentration indices. The command also graphs concentration curves (and Lorenz curves) and performs statistical inference for the comparison of inequality between groups. The article offers an accessible introduction to the various concentration indices that have been proposed to suit different measurement scales and ethical responses to inequality. The command's capabilities and syntax are demonstrated through analysis of wealth-related inequality in health and healthcare in Cambodia.

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References

Wagstaff A, Watanabe N . What difference does the choice of SES make in health inequality measurement?. Health Econ. 2003; 12(10):885-90. DOI: 10.1002/hec.805. View

Doorslaer E, Wagstaff A, Bleichrodt H, Calonge S, Gerdtham U, Gerfin M . Income-related inequalities in health: some international comparisons. J Health Econ. 1997; 16(1):93-112. DOI: 10.1016/s0167-6296(96)00532-2. View

Wagstaff A . Socioeconomic inequalities in child mortality: comparisons across nine developing countries. Bull World Health Organ. 2000; 78(1):19-29. PMC: 2560599. View

Erreygers G, Van Ourti T . Putting the cart before the horse. A comment on Wagstaff on inequality measurement in the presence of binary variables. Health Econ. 2011; 20(10):1161-5. PMC: 3304083. DOI: 10.1002/hec.1754. View

Kjellsson G, Gerdtham U . On correcting the concentration index for binary variables. J Health Econ. 2013; 32(3):659-70. DOI: 10.1016/j.jhealeco.2012.10.012. View

Erreygers G, Clarke P, Van Ourti T . "Mirror, mirror, on the wall, who in this land is fairest of all?"--Distributional sensitivity in the measurement of socioeconomic inequality of health. J Health Econ. 2011; 31(1):257-70. PMC: 3349439. DOI: 10.1016/j.jhealeco.2011.10.009. View

Wagstaff A . The bounds of the concentration index when the variable of interest is binary, with an application to immunization inequality. Health Econ. 2004; 14(4):429-32. DOI: 10.1002/hec.953. View

Lambert P, Zheng B . On the consistent measurement of attainment and shortfall inequality. J Health Econ. 2010; 30(1):214-9. DOI: 10.1016/j.jhealeco.2010.10.008. View

Wagstaff A . Inequality aversion, health inequalities and health achievement. J Health Econ. 2002; 21(4):627-41. DOI: 10.1016/s0167-6296(02)00006-1. View

10.

van Doorslaer E, Masseria C, Koolman X . Inequalities in access to medical care by income in developed countries. CMAJ. 2006; 174(2):177-83. PMC: 1329455. DOI: 10.1503/cmaj.050584. View

11.

Pereira J . Inequality in infant mortality in Portugal, 1971-1991. Dev Health Econ Public Policy. 2000; 6:75-93. View

12.

Bosmans K . Consistent Comparisons of Attainment and Shortfall Inequality: A Critical Examination. Health Econ. 2015; 25(11):1425-1432. DOI: 10.1002/hec.3228. View

13.

Wagstaff A . Correcting the concentration index: a comment. J Health Econ. 2009; 28(2):516-20, author reply 521-4. DOI: 10.1016/j.jhealeco.2008.12.003. View

14.

Bleichrodt H, van Doorslaer E . A welfare economics foundation for health inequality measurement. J Health Econ. 2006; 25(5):945-57. DOI: 10.1016/j.jhealeco.2006.01.002. View

15.

Wagstaff A, Paci P, Doorslaer E . On the measurement of inequalities in health. Soc Sci Med. 1991; 33(5):545-57. DOI: 10.1016/0277-9536(91)90212-u. View

16.

Clarke P, Gerdtham U, Johannesson M, Bingefors K, Smith L . On the measurement of relative and absolute income-related health inequality. Soc Sci Med. 2002; 55(11):1923-8. DOI: 10.1016/s0277-9536(01)00321-5. View

17.

Wagstaff A . Reply to Guido Erreygers and Tom Van Ourti's comment on 'The concentration index of a binary outcome revisited'. Health Econ. 2011; 20(10):1166-8. DOI: 10.1002/hec.1753. View

18.

Van Ourti T . Measuring horizontal inequity in Belgian health care using a Gaussian random effects two part count data model. Health Econ. 2004; 13(7):705-24. DOI: 10.1002/hec.920. View

19.

Filmer D, Pritchett L . Estimating wealth effects without expenditure data--or tears: an application to educational enrollments in states of India. Demography. 2001; 38(1):115-32. DOI: 10.1353/dem.2001.0003. View

20.

Wagstaff A . The concentration index of a binary outcome revisited. Health Econ. 2011; 20(10):1155-60. DOI: 10.1002/hec.1752. View