Lorenz Curve

http://www.unc.edu/~nielsen/special/s2/s2.htm

A lorenz curve is a graph in which the cumulative percentage of some variable is plotted against the cumulative percentage of the corresponding population.  The extent to which the curve sags below a straight diagonal line indicates the degree of inequality of distribution.  The 45 degree line represents perfect equality so the closer the Lorenz curve is to the 45 degree line, the less the inequality and the smaller the inequality, or Gini coefficient.