In the 19th century, tsarist censors banned John Stuart Mill’s On Liberty while letting through Karl Marx’s Das Kapital. Mill’s message was so lucidly expressed that it posed an obvious and immediate threat to the regime; Marx’s prose was clotted and convoluted and his economics littered with leftovers from his youthful enthusiasm for Hegel. Thomas Piketty’s Capital in the Twenty-First Century shares its title with Marx’s work but its argumentative verve with Mill’s, and it has been a runaway bestseller in the United States. In spite of the efforts of conservative American economists to persuade their readers that anyone who raises questions about inequalities of income and wealth must be a Marxist, Piketty has no time whatsoever for Marx. Piketty’s economics is ‘data driven’, while Marx was short of useful data, did not make good use of what data he had and generalised wildly from a few exceptional cases of capital-intensive industries, such as Manchester textile manufacturing.