Capital in the Twenty-First Century is a 2013 book by French economist Thomas Piketty. It focuses on wealth and income inequality in Europe and the United States since the 18th century. It was initially published in French (as Le Capital au XXIe siècle) in August 2013; an English translation by Arthur Goldhammer followed in April 2014.[1]

The book's central thesis is that when the rate of return on capital (r) is greater than the rate of economic growth (g) over the long term, the result is concentration of wealth, and this unequal distribution of wealth causes social and economic instability. Piketty proposes a global system of progressive wealth taxes to help reduce inequality and avoid the vast majority of wealth coming under the control of a tiny minority.

What is the Gini Index?
The Gini index or Gini coefficient is a statistical measure of distribution developed by the Italian statistician Corrado Gini in 1912. It is often used as a gauge of economic inequality, measuring income distribution or, less commonly, wealth distribution among a population. The coefficient ranges from 0 (or 0%) to 1 (or 100%), with 0 representing perfect equality and 1 representing perfect inequality. Values over 1 are theoretically possible due to negative income or wealth.