The United States and China together account for about 42% of world GDP, and the top 20 economies produce roughly 80% of global output — leaving more than 170 other economies to share the remaining fifth.

The measurement basis matters more than most rankings admit. This list uses nominal US dollars; switch to purchasing power parity and China moves ahead of the United States while India jumps from sixth to third. Same countries, two entirely different orders.

The standings are also more fragile than they look: Japan, the UK, and India sit within 6% of one another at fourth through sixth, Australia leads Mexico by just 0.15%, and 20th-placed Switzerland is only about 1% ahead of Poland. A single currency swing can reshuffle any of them.