The United States has the largest economy in the world, by traditional GDP measures.

But when adjustments are made to account for Purchase Price Parity, and the cost differences for similar products, it is China with the largest economy.

The United States has a giant services sector, and includes careers that have no equivalent in other countries. The massive legal, finance, insurance, real estate brokerage, and lobbying industries are far larger in the US than in any other country.

When economists remove those sectors from the calculation of GDP, the result is "Productive GDP", and involves accounting only for the production of tangible products in the economy.