Lorenz Curve

http://www.geoib.com/lorenz-curve.html

The Lorenz Curve is a graphical method used to display the concentration of activities within an area. The Lorenz Curve above shows the distribution of wealth in two different countries, as compared to a line of perfectly equal distribution. That line is an ideal used as a comparison for real-world values. In a perfectly even distribution of wealth, 60% of the cumulative population would control 60% of the cumulative wealth. In the above example, 60% of the population controls only 20% of the wealth. This graphing method could provide information that would be useful in geography and cartography.