Bandingkan kaedah

	Concentration Curve and Index	Concentration Index
Bidang	Ekonomi	Social Epidemiology
Keluarga	Process / pipeline	Process / pipeline
Tahun asal	1991	1991
Pengasas	Adam Wagstaff, Pierella Paci & Eddy van Doorslaer	Adam Wagstaff, Pierfilippo Paci & Eddy van Doorslaer; Nanak Kakwani
Jenis	Bivariate inequality measure	Rank-based summary index of socioeconomic inequality in health
Sumber perintis	Wagstaff, A., Paci, P., & van Doorslaer, E. (1991). On the measurement of inequalities in health. Social Science & Medicine, 33(5), 545–557.	Wagstaff, A., Paci, P., & van Doorslaer, E. (1991). On the measurement of inequalities in health. Social Science & Medicine, 33(5), 545-557.
Alias	Health Concentration Index, Concentration Curve, Socioeconomic Inequality in Health Index, Wagstaff Index	Health Concentration Index, Concentration Curve and Index, Wagstaff Concentration Index, Erreygers Corrected Concentration Index
Berkaitan	3	4
Ringkasan	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 concentration index is the standard summary measure of socioeconomic inequality in health: it quantifies the degree to which a health outcome - illness, mortality, malnutrition, or healthcare use - is disproportionately concentrated among the poor or the rich. It is built from the concentration curve, which plots the cumulative share of health against the cumulative share of the population ranked from poorest to richest, and the index is simply twice the area between that curve and the line of perfect equality. Wagstaff, Paci, and van Doorslaer's 1991 critique of inequality measures argued that, unlike the simple range or the Gini, the concentration index properly reflects the socioeconomic dimension of health inequality and the experience of the whole distribution. Kakwani, Wagstaff, and van Doorslaer's 1997 paper then supplied a computational formula, a convenient regression estimator, and the asymptotic variance needed for statistical inference. The index ranges from minus one to plus one, with zero meaning no socioeconomic gradient, a negative value meaning ill health concentrates among the poor, and a positive value the reverse. It has become the lingua franca of health-equity monitoring at agencies like the World Bank and WHO.