In the depths of the 1930s depression, John Maynard Keynes wrote an essay looking ahead through the immediate difficulties to a time when production would have increased so much that the economic problem would be solved and the people could concentrate on higher things such as personal relations, the arts and leisure.

The magic of compound growth could, Keynes asserted, make us eight times better off in 100 years relative to where we were in his base year, 1929. Output per capita has indeed since grown in most western countries in line with Keynes’s expectations. Yet the promised land still seems far off.