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	Palma Ratio	Lorenz Curve
Field	Sociology	Sociology
Family	Process / pipeline	Process / pipeline
Year of origin	2011 (Palma's finding); 2013–2014 (the ratio)	1905
Originator	Gabriel Palma; named by Cobham & Sumner	Max Otto Lorenz
Type	Tail-ratio inequality measure	Graphical representation of distributional inequality
Seminal source	Cobham, A., & Sumner, A. (2014). Is inequality all about the tails? The Palma measure of income inequality. Significance, 11(1), 10–13.	Lorenz, M. O. (1905). Methods of measuring the concentration of wealth. Publications of the American Statistical Association, 9(70), 209–219.
Aliases	Palma index, Palma measure, top10/bottom40 ratio	Lorenz concentration curve, Lorenz diagram, cumulative share curve
Related	5	5
Summary	The Palma ratio measures income inequality as the ratio of the income share held by the richest 10 percent of the population to the share held by the poorest 40 percent. It rests on the empirical regularity, documented by Gabriel Palma, that the middle deciles (5 through 9) capture a remarkably stable half of national income across countries, so that inequality is essentially a contest between the top and the bottom — the 'tails' of the distribution.	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.