Why economists compare the price of a burger
The Big Mac Index turns a familiar meal into a rough test of whether currencies are priced similarly. The idea rests on purchasing power parity: over time, exchange rates should tend to reflect how much money buys in different countries. If a Big Mac costs much more in one country than another after converting prices into the same currency, that may suggest the first country’s currency is expensive relative to the second.
The burger is useful because McDonald’s sells a broadly similar product in many places, giving the comparison a recognizable common item. The index, introduced by The Economist in 1986, makes an abstract exchange-rate concept easy to picture: how much local money does it take to buy the same sort of lunch?
What the price captures—and what it can’t
A burger’s price is not just the cost of beef and bread. It also reflects local wages, rents, taxes, ingredient costs, and the expense of running a restaurant. Those local costs help explain why a Big Mac can be cheaper in one country without its currency necessarily being undervalued in the way a simple price comparison implies.
Nor is the product perfectly identical everywhere. Recipes and serving details can vary, and a restaurant meal is not a basket of goods that can be freely traded across borders. Economists therefore treat the index as an illustrative signal, not a precise exchange-rate verdict. Its value is that it makes purchasing power differences tangible—and offers a memorable starting point for asking why currencies buy different amounts in different places.
