WHEN the first volume of Karl Marx’s “Das Kapital” was published in 1867, it took five years to sell 1,000 copies in its original German. It was not translated into English for two decades, and this newspaper did not see fit to mention it until 1907. By comparison, Thomas Piketty’s “Capital in the Twenty-First Century” is an overnight sensation. Originally published in French (when we first reviewed it), Mr Piketty’s vast tome on income-and-wealth distribution has become a bestseller since the English translation appeared in March. In America it is the top-selling book on Amazon, fiction included.

The book’s success has a lot to do with being about the right subject at the right time. Inequality has suddenly become a fevered topic, especially in America. Having for years dismissed the gaps between the haves and have-nots as a European obsession, Americans, stung by the excesses of Wall Street, are suddenly talking about the rich and redistribution. Hence the attraction of a book which argues that growing wealth concentration is inherent to capitalism and recommends a global tax on wealth as the progressive solution.

“Capital” has duly enraptured the left, infuriated the right and spiced up the dismal science in the popular mind (see article). But if Mr Piketty does set the tone of debate on inequality, the world will be the poorer for it. For like its 19th-century namesake, “Capital” contains some marvellous scholarship, but as a guide to action, is deeply flawed.

“Capital” makes three big contributions in its 577 pages. First, Mr Piketty, a pioneer in using tax statistics to measure inequality, painstakingly documents the evolution of income and wealth over the past 300 years, particularly in Europe and America. In doing so, he shows that the period from about 1914 to the 1970s was an historical outlier in which both income inequality and the stock of wealth (relative to annual national income) fell dramatically. Since the 1970s both wealth and income gaps have been rising back towards their pre-20th-century norms. There are surely a few snafus in these statistics, but this work has transformed understanding of the history of wealth, with eye-popping results. Who knew, for instance, that the annual value of inheritances in France has tripled from less than 5% of GDP in the 1950s to about 15%, not all that far from the 19th-century peak of 25%? As a piece of empirical sleuthing, the book is indisputably brilliant.

Mr Piketty’s second contribution is to come up with a theory of capitalism that explains these facts and offers a prediction of where wealth distribution is heading. His central claim is that the free-market system has a natural tendency towards increasing the concentration of wealth, because the rate of return on property and investments has consistently been higher than the rate of economic growth. Two world wars, the Depression and high taxes pushed down the return on wealth in the 20th century, while rapid productivity and population rises pushed up growth. But without such countervailing factors, Mr Piketty argues, higher returns on capital will concentrate wealth—especially when, as now, an ageing population means that growth should slow.

Mr Piketty’s expectation of rising wealth concentration is not outlandish. However, it is a prediction based on extrapolating from the past, not an inherent model of capitalism. He assumes that the returns to capital will not fall substantially even as the stock of wealth rises. That may prove to be true, but the Piketty prediction is a hypothesis, not an iron law.

Nit-Piketty

That is where the problems start, because Mr Piketty’s third contribution is to offer policy proposals that assume this growing concentration of wealth is not only inevitable, but the thing that matters most. He prescribes a progressive global tax on capital (an annual levy that could start at 0.1% and hits a maximum of perhaps 10% on the greatest fortunes). He also suggests a punitive 80% tax rate on incomes above $500,000 or so.

Here “Capital” drifts to the left and loses credibility. Mr Piketty asserts rather than explains why tempering wealth concentration should be the priority (as opposed to, say, boosting growth). He barely acknowledges any trade-offs or costs to his redistributionist agenda. Most economists, common sense and a lot of French businesspeople would argue that higher taxes on income and wealth put off entrepreneurs and risk taking; he blithely dismisses that. And his to-do list is oddly blinkered in its focus on taxing the rich. He ignores ways to broaden the ownership of capital, from “baby bonds” to government top-ups of private saving accounts. Some capital taxes could sit nicely in a sensible 21st-century policy toolkit (inheritance taxes, in particular), but they are not the only, or even the main, way to ensure broad-based prosperity.

Mr Piketty’s focus on soaking the rich smacks of socialist ideology, not scholarship. That may explain why “Capital” is a bestseller. But it is a poor blueprint for action.