L’ultimo episodio di Planet Money, il podcast di economia di NPR.

There’s one statistic that rules them all when it comes to keeping track of the economy: gross domestic product (GDP). It’s the sum of all final transactions, so all the goods or services bought and sold, in an economy. GDP tells us how hot the economy is running, or how cool — like if we might be heading into a recession. And it’s an important tool to compare countries, policies, and politicians. It’s used by the U.S. government to allocate money and by businesses to make decisions about the future.

For close to a century the building blocks of GDP have been the same. Though there have been updates to the methodology behind calculating it. The U.S. Bureau of Economic Analysis, the federal agency that calculates it, is constantly tweaking their process to make GDP accurately reflect the changing economy.