Accumulative line graph or Lorenz curve

In economics, the Lorenz curve is a graphical representation of the proportion of thedata assumed by the bottom y values. It is often used to represent income distribution, where it shows for the bottom x of values. The percentage of households is plotted on the x-axis, the percentage of income on the y-axis. It can also be used to show distribution of assets. "In such use, many economists consider it to be a measure of social inequality. It was developed by Max O. Lorenz in 1905 for representing inequality of the wealth distribution." The concept is useful in describing inequality among the size of individuals in ecology, and in studies of biodiversity. It is also useful in business modeling and in consumer finance.

Max O. Lorenz

Max Otto Lorenz was an American economist who developed the Lorenz curve in 1905 to describe income inequalities. He published this paper while a doctoral student at the University of Wisconsin–Madison...

http://www.absoluteastronomy.com/topics/Lorenz_curve