Gini Coefficient
Definition
From the Wikipedia:
"The Gini coefficient is a measure of statistical dispersion developed by the Italian statistician Corrado Gini and published in his 1912 paper "Variability and Mutability" (Italian: Variabilità e mutabilità). It is commonly used as a measure of inequality of income or wealth. It has, however, also found application in the study of inequalities in disciplines as diverse as health science, ecology, chemistry and engineering." (http://en.wikipedia.org/wiki/Gini_coefficient)