The Hoover index, also known as the Robin Hood index, but better known as the Schutz index, is a measure of income metrics. It is equal to the portion of the total community income that would have to be redistributed (taken from the richer half of the population and given to the poorer half) for there to be income uniformity.
It can be graphically represented as the longest vertical distance between the Lorenz curve, or the cumulative portion of the total income held below a certain income percentile, and the 45 degree line representing perfect equality.
The Hoover index is typically used in applications related to socioeconomic class (SES) and health. It is conceptually one of the simplest inequality indices used in econometrics. A better known inequality measure is the Gini coefficient which is also based on the Lorenz curve.
Contents

Computation 1

See also 2

Notes 3

Further reading 4

External links 5
Computation
For the formula, a notation^{[1]} is used, where the amount N of quantiles only appears as upper border of summations. Thus, inequities can be computed for quantiles with different widths A. For example, E_i could be the income in the quantile #i and A_i could be the amount (absolute or relative) of earners in the quantile #i. E_\text{total} then would be the sum of incomes of all N quantiles and A_\text{total} would be the sum of the income earners in all N quantiles.
Computation of the Robin Hood index H:

H = {\frac{1}{2}} \sum_{i=1}^N \left {\frac}  {\frac} \right.
For comparison,^{[2]} here also the computation of the symmetrized Theil index T_s is given:

T_s = {\frac{1}{2}} \sum_{i=1}^N \ln{\frac \left({\frac}  {\frac} \right).
Both formulas can be used in spreadsheet computations.
See also
Notes

^ The notation using E and A follows the notation of a small calculation published by Lionnel Maugis: Inequality Measures in Mathematical Programming for the Air Traffic Flow Management Problem with EnRoute Capacities (für IFORS 96), 1996

^ For an explanation of the comparison with Henri Theil's index see: Theil index
Further reading

Edgar Malone Hoover jr. (1936) The Measurement of Industrial Localization, Review of Economics and Statistics, 18, No. 162171

Edgar Malone Hoover jr. (1984) An Introduction to Regional Economics, 1984, ISBN 0075544407

Philip B. Coulter: (1989) Measuring Inequality, ISBN 0813377269 (This book describes about 50 different inequality measures  it's a good guide, but it contains some mistakes, so watch out.)

Robert Sapolsky (2005) Sick of Poverty, Scientific American, December 2005

Bruce P Kennedy, Ichiro Kawachi, Deborah ProthrowStith (1996) Income distribution and mortality: cross sectional ecological study of the Robin Hood index in the United States, BMJ 312:10041007
External links

Free Inequality Calculator: Online and downloadable scripts (Python and Lua) for Atkinson, Gini, and Hoover inequalities
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