What defines the west? American and European politicians like to talk about values and institutions. But for billions of people around the world, the crucial point is simpler and easier to grasp. The west is the part of the world where even ordinary people live comfortably. That is the dream that makes illegal immigrants risk their lives, trying to get into Europe or the US.

Yet, even though the lure of the west remains intense, the western world itself is losing faith in its future. Last week Barack Obama gave one of the bleakest speeches of his presidency. In unsparing terms, the US president chronicled the increasing inequality and declining social mobility that, he says, “pose a fundamental threat to the American dream, our way of life and what we stand for around the world”.

A Pew Research Center opinion survey, conducted in 39 countries this spring, asked: “Will children in your country be better off than their parents?” Only 33 per cent of Americans believed their children would live better, while 62 per cent said they would live worse. Europeans were even gloomier. Just 28 per cent of Germans, 17 per cent of Brits, 14 per cent of Italians and 9 per cent of French thought their children would be better off than previous generations. This western pessimism contrasts strongly with optimism in the developing world: 82 per cent of Chinese, 59 per cent of Indians and 65 per cent of Nigerians believe in a more prosperous future.