The widening of income gaps is a reversal of the pattern in much of the 20th century, when inequality narrowed in many countries. That narrowing seemed so inevitable that Simon Kuznets, a Belarusian-born Harvard economist, in 1955 famously described the relationship between inequality and prosperity as an upside-down U. According to the “Kuznets curve”, inequality rises in the early stages of industrialisation as people leave the land, become more productive and earn more in factories. Once industrialisation is complete and better-educated citizens demand redistribution from their government, it declines again.
Until 1980 this prediction appeared to have been vindicated. But the past 30 years have put paid to the Kuznets curve, at least in advanced economies. These days the inverted U has turned into something closer to an italicised N, with the final stroke pointing menacingly upwards.