Thomas Piketty

Piketty specializes in economic inequality, taking a historic and statistical approach. His work looks at the rate of capital accumulation in relation to economic growth over a two hundred year spread from the nineteenth century to the present. His novel use of tax records enabled him to gather data on the very top economic elite, who had previously been understudied, and to ascertain their rate of accumulation of wealth and how this compared to the rest of society and economy. His most recent book, Capital in the Twenty-First Century, relies on economic data going back 250 years to show that an ever-rising concentration of wealth is not self-correcting. To address this problem, he proposes redistribution through a progressive global tax on wealth.

A research project on high incomes in France led to the book Les hauts revenus en France au XXe siècle (High incomes in France in the 20th Century, Grasset, 2001), which was based on a survey of statistical series covering the whole of the 20th century, built from data from the fiscal services (particularly income tax declarations). He extended this analysis in his immensely popular book Le Capital au XXIe siècle (Capital in the Twenty-First Century). A study by Emmanuel Saez and Piketty showed that the top 10 percent of earners took more than half of the country's total income in 2012, the highest level recorded since the government began collecting the relevant data a century ago.

Piketty's work shows that differences in earnings dropped sharply during the 20th century in France, mostly after World War II. He argues that this was due to a decrease in estate inequalities, while wage inequalities remained stable. The shrinking inequality during this period, Piketty says, resulted from a highly progressive income tax after the war, which upset the dynamics of estate accumulation by reducing the surplus money available for saving by the wealthiest.^{[citation needed]}

The normative conclusion Piketty draws is that a tax cut and thus a decrease in the financial contribution to society of the wealthy that has been happening in France since the late 1990s will assist in the rebuilding of the earlier large fortunes of the rentier class. This trend will lead to the rise of what he calls patrimonial capitalism, in which a few families control most of the wealth.