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	Concentration Curve and Index	Lorenz Curve
Field	Economics	Sociology
Family	Process / pipeline	Process / pipeline
Year of origin	1991	1905
Originator	Adam Wagstaff, Pierella Paci & Eddy van Doorslaer	Max Otto Lorenz
Type	Bivariate inequality measure	Graphical representation of distributional inequality
Seminal source	Wagstaff, A., Paci, P., & van Doorslaer, E. (1991). On the measurement of inequalities in health. Social Science & Medicine, 33(5), 545–557.	Lorenz, M. O. (1905). Methods of measuring the concentration of wealth. Publications of the American Statistical Association, 9(70), 209–219.
Aliases	Health Concentration Index, Concentration Curve, Socioeconomic Inequality in Health Index, Wagstaff Index	Lorenz concentration curve, Lorenz diagram, cumulative share curve
Related	3	5
Summary	The concentration curve and concentration index, established as the standard tools for measuring socioeconomic inequality in health by Wagstaff, Paci, and van Doorslaer in 1991, capture how a health variable is distributed across the population ranked by socioeconomic status. The concentration curve plots the cumulative share of health (or ill-health) against the cumulative share of people ordered from poorest to richest; the concentration index is twice the area between this curve and the line of equality. Unlike the Gini coefficient, which measures pure dispersion, the concentration index is bivariate — it measures inequality in one variable that is systematically related to a second, socioeconomic ranking.	The Lorenz curve is a graphical device that displays the full shape of inequality in a distribution by plotting the cumulative share of a quantity (such as income) held by the cumulative share of the population, ranked from poorest to richest. Introduced by Max Lorenz in 1905, it underlies the Gini coefficient and provides the basis for ranking distributions by inequality when one curve lies entirely above another.