The total market value of all goods and services a country produces in a year, and the single most powerful number in modern governance. GDP made the economy legible as one steerable figure — an indispensable tool that, precisely because it became the goal, quietly defined what counts as progress and what does not.
In 1934, an economist named Simon Kuznets handed Congress a report that tried to add up everything the United States had produced in a year. He built the number in part to show how badly the Depression had hurt the country. Then he added a warning: this figure could not measure the welfare of a nation. Governments spent the next ninety years ignoring that warning. The number he helped invent became the most watched statistic in the world — a single figure that tells politicians whether to act, reassures markets, and decides elections. The trouble is that it was never designed to do any of those things.