Thomas Piketty

In 'Capital in the Twenty-First Century,' Piketty argues that when the rate of return on capital (r) persistently exceeds the overall rate of economic growth (g), wealth concentrates increasingly in the hands of existing asset owners. He assembled over two centuries of tax and inheritance data, primarily from France, the United Kingdom, and the United States, to support this thesis.

The book was first published in French in 2013 and then in English by Harvard University Press in 2014, becoming an unexpected international bestseller that sold over two million copies. Its English translation by Arthur Goldhammer made Piketty's long-run inequality data accessible to a mainstream global audience.

Piketty advocates for a progressive global tax on capital as the primary structural response to rising wealth concentration, while acknowledging the enormous political and coordination challenges involved. He also supports greater transparency in financial data, more progressive income taxation, and democratic pressure on tax havens.

Critics including Financial Times economics editor Chris Giles challenged specific data points and adjustments in Piketty's European wealth series, while economists such as MIT's Robert Solow broadly accepted the data but debated interpretation. Others argued that the relationship between r and g is less mechanically deterministic than the book suggests, since capital returns vary widely by asset class.