Abstract: The author shows how a quick approximation of the Lorenz curve's Gini coefficient can be calculated empirically using numerical data presented in cumulative income quintiles. When the technique here was used to estimate 621 income quintile/Gini coefficient observations from the Deninger and Squire/World Bank data set, this approach performed better than a popular alternative, the trapezoidal rule.

Keywords: geometric approach, Gini coefficient, Lorenz curve, trapezoidal rule JEL codes: A22, C63, D31

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I offer a quick method, called the Z-gradient rule, for approximating the Lorenz curve's Gini coefficient, using numerical quintile data. (1) ...