Robin Hood index

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The Robin Hood index is a measurement of income inequality across a geographic area and is derived from the Lorenz curve.

Mathematically, the Robin Hood index for Lorenz curve $\scriptstyle L(x)$ is $\scriptstyle \max (x - L(x))$ . This means that the index is derived by finding the largest vertical line, which can be drawn between a Lorenz curve for perfectly even distribution (e.g. of incomes) and the measured Lorenz curve. Theoretically the height of the rectangle surrounding the Lorenz curve is the greatest possible maximum. Therefore dividing the found line by the height of the rectangle yields a metric between 0% and 100%.