Doing less with more

COUNTRIES grow richer when they learn how to produce more valuable stuff per person. Sadly, many advanced economies seem to have lost the knack. Except for a brief spurt around the turn of the millennium, productivity has grown painfully slowly in rich countries over the last four decades (see chart)--a factor, economists reckon, that has contributed to stagnant pay. Labour productivity in America fell at a startling 2.2% annual pace in the fourth quarter of 2015; growth of 0.6% for the year as a whole was better, but hardly impressive. Orthodox explanations for the problem tend to fall into one of three categories.