When the world’s richest countries were booming, few people worried overmuch that the top 1 per cent were enjoying an ever-growing share of that prosperity. In the wake of a depression in the US, a fiscal chasm in the UK and an existential crisis in the eurozone – and the shaming of the world’s bankers – worrying about inequality is no longer the preserve of the far left.

There should be no doubt about the facts: the income share of the top 1 per cent has roughly doubled in the US since the early 1970s, and is now about 20 per cent. Much the same trend can be seen in Australia, Canada and the UK – although in each case the income share of the top 1 per cent is smaller. In France, Germany and Japan there seems to be no such trend. (The source is the World Top Incomes Database, summarised in the opening paper of a superb symposium in this summer’s Journal of Economic Perspectives.)

But should we care? There are two reasons we might: process and outcome. We might worry that the gains of the rich are ill gotten: the result of the old-boy network, or fraud, or exploiting the largesse of the taxpayer. Or we might worry that the results are noxious: misery and envy, or ill health, or dysfunctional democracy, or slow growth as the rich sit on their cash, or excessive debt and thus financial instability.