You can see the computer age everywhere but in the productivity statistics.” Today, we could repeat this celebrated 1987 statement by Robert Solow, Nobel laureate founder of modern growth theory, with the substitution of “technology” for “computer”.

We live in an age judged to be one of exciting technological change, but our national accounts tell us that productivity is almost stagnant. Is the slowdown or the innovation an illusion? If not, what might explain the puzzle?

The slowdown, if true, matters. As Paul Krugman, also a Nobel laureate, argued, “Productivity isn’t everything, but in the long run it is almost everything.” Improvements in standards of living depend almost entirely on rising output per worker. The productivity slowdown is a major explanation for the stagnation in real incomes and the pressure for fiscal austerity in high-income countries. Gene Grossman of Princeton and three co-authors even argue that the marked slowdown in the growth of incomes per head also explains the decline in labour’s share of national income in wealthy countries.