B ILLIONAIRES HAVE never exactly been popular with the radical left. But with a member of the nine-zero club sitting in the White House, and a decade of slow growth in living standards, some Democrats have taken to attacking billionaires to draw attention to their argument for root-and-branch economic reform. “Billionaires should not exist,” says Bernie Sanders, a presidential candidate. Plutocrat-bashing has become part of the debate in Britain, too, where an election will be held on December 12th. At the Labour Party’s campaign opener Jeremy Corbyn, its far-left leader, attacked the Duke of Westminster, one of Britain’s wealthiest landowners, and Rupert Murdoch, a media mogul.

Socialists argue that anyone who has become fantastically rich has profited from a rigged system. “Every billionaire is a policy failure,” goes the memorable phrase. To assess this claim The Economist has drawn on data from Forbes, a business magazine, on billionaires in the rich world, updating an index of crony capitalism that we first put together in 2014 (see chart).

In the past decade the wealth of the world’s 2,200-odd plutocrats (which puts them inside the world’s top 0.0001%) has risen much faster than global GDP . Still, most of the world’s billionaire wealth has been earned fair and square. Oprah Winfrey, for instance, has a fortune of about $3bn. It is one thing to feel that having so much money is distasteful. It is quite another to argue that these people have accumulated their wealth illegitimately and should be stripped of it.