America is immersed in a deep and troubling paradox. By most conventional measures, Americans have never had it so good. The economy is entering its fifth year of high growth and is close to achieving full employment.

Yet Americans tell pollsters they have rarely felt so anxious about their future. Nearly 70 per cent say they believe their country is heading in the wrong direction. According to one recent poll, a narrow majority believe their children will be worse off than they are. If, as the saying goes, America’s national religion is optimism, the country’s faith is wavering. Why now?