How to measure prosperity

WHICH would you prefer to be: a medieval monarch or a modern office-worker? The king has armies of servants. He wears the finest silks and eats the richest foods. But he is also a martyr to toothache. He is prone to fatal infections. It takes him a week by carriage to travel between palaces. And he is tired of listening to the same jesters. Life as a 21st-century office drone looks more appealing once you think about modern dentistry, antibiotics, air travel, smartphones and YouTube.The question is more than just a parlour game. It shows how tricky it is to compare living standards over time. Yet such comparisons are not just routinely made, but rely heavily on a single metric: gross domestic product (GDP). This one number has become shorthand for material well-being, even though it is a deeply flawed gauge of prosperity, and getting worse all the time (see ). That may in turn be distorting levels of anxiety in the rich world about everything from stagnant incomes to disappointing productivity growth.