The New Theories of Economics

Vilfredo Federico Damaso Pareto 1848 –  1923), born Wilfried Fritz Pareto, was an Italian engineer, sociologist, economist, political scientist and philosopher. He made several important contributions to economics, particularly in the study of income distribution and in the analysis of individuals' choices, helping economics evolve from a branch of moral philosophy as practiced by Adam Smith into a data intensive field of scientific research and mathematical equations. His books look more like modern economics than most other texts of that day: tables of statistics from across the world and ages, rows of integral signs and equations, intricate charts and graphs." He also introduced the concept of Pareto efficiency and helped develop the field of microeconomics by becoming the first to discover that income follows a Pareto distribution, which is a power law probability distribution. The Pareto principle was named after him and built on observations of his such as that 80% of the land in Italy was owned by 20% of the population. 

Pareto’s principles are spelled out in his short essay, The New Theories of Economics.