The Big Mac became the basis for The Economist's Big Mac Index, created in 1986.
The Big Mac Index compares the prices of the same McDonald's hamburger in different countries. The Economist introduced it in 1986 as an informal way to illustrate purchasing-power parity, the economic idea that exchange rates should eventually make comparable goods cost about the same in different markets.
The Big Mac was chosen because McDonald's sells it in many countries and prepares it from a broadly standardized recipe. Its price is not a perfect economic measurement: local wages, rents, taxes, supply chains, tariffs, and ingredients all affect the final cost. Even so, the product's international visibility makes the index accessible to a general audience.
The index is a branding-history connection as well as an economics story. A menu item became a globally recognized reference point, showing how McDonald's product names can travel beyond advertising and enter everyday discussions of currency and prices.