Vilfredo Pareto (July 15, 1848 - August 19, 1923) made several important contributions to economics, sociology and moral philosophy, especially in the study of income distribution and in the analysis of individuals' choices. He introduced the concept of Pareto efficiency and helped develop the field of microeconomics with ideas such as indifference curves.
He is well known for the observation that 20% of the population owned 80% of the property in Italy, later generalised (by Joseph Juran and others) into the Pareto principle, and generalised further to the concept of a Pareto distribution.
The Pareto index is a measure of the inequality of income distribution.
Pareto's social policies were put on paper in his work, "Mind and Society", which is sometimes criticized as being elitist.