What Counts in GDP

GDP, gross domestic product, is a running total of new production. To keep that total honest, it counts only final goods, the ones bought by their end user, and leaves out intermediate goods, the inputs businesses buy from each other to make something else. A steelmaker selling steel to a car company, which sells the car to you, only shows up once in GDP: in the final price of the car. That final price already has the cost of the steel baked into it, so counting the steel sale separately would count the same value twice. This is why a used car sale adds nothing new: that car's value was already counted the year it rolled off the factory line. Selling it again just transfers ownership of something that already exists.

Financial transactions get excluded for a similar reason. Buying a stock, trading a bond, or watching your portfolio grow doesn't create a new good or service, it just moves claims on wealth between people, or repriced existing assets. GDP cares about production, not about who owns what or what it's currently worth on paper.

This also explains why GDP misses a lot of real activity. Unpaid household work, like cleaning your own house, parenting, or growing vegetables in your backyard, never enters a market, so it's invisible to GDP even though it produces real value. When a homeowner fires the cleaner and starts cleaning the house themselves, measured GDP actually falls, even though the house is just as clean. That gap between what GDP measures and what the economy actually produces matters once you start using GDP to judge living standards or compare countries, a theme that carries into how GDP is built up from income and expenditure in the next topics.