The Economist's Big Mac index has compared the price of a Big Mac across the globe since 1986. It applies the economic principle of purchasing-power parity: a currency's value should reflect the amount of stuff it can buy, and if the same good costs different amounts in different countries at market exchange rates, currencies are misaligned. The index relies on the zealous commitment to consistency of the McDonald's Corporation to ensure the sameness of the product across countries.
A more rigorous version of the same idea is the International Comparison Programme, led by the World Bank, which prices hundreds of items fastidiously defined for cross-border comparability. It is one of the world's largest statistical initiatives.
In Japan a Big Mac costs ¥480 on average, working out at only about $3 at market exchange rates—roughly half the price of the same burger in America ($6.12). The index suggests the yen is roughly 50% undervalued. China's Big Macs cost $3.66, implying the yuan is 40% undervalued. In India, McDonald's does not serve beef burgers; its Maharaja Mac, featuring a double chicken patty fortified with jalapeños and habanero sauce, is $2.51. The dollar is overvalued against 49 of 70 currencies (see dollar dominance).
The undervaluation of India's rupee has worsened over the past year as the currency has continued sliding. China's yuan has actually strengthened against the dollar in the past year, but movements in foreign-exchange markets have been offset by contrary trends in burger prices: a Big Mac in China costs the same now as it did in January 2025, while America's Big Mac has risen in price.
In 1987 officials from the world's biggest economies negotiated the Louvre Accord to arrest the dollar's decline; they accompanied their deliberations with a turbot soufflé cardinale and fine wine from the cellar of France's finance ministry. Donald Trump has signalled support for Japan's attempt to strengthen the yen, but today's ad hoc interventions are more like fast food to go than the grand currency diplomacy of the 1980s.
You may be sure that when a man begins to call himself a "realist," he is preparing to do something he is secretly ashamed of doing.