Purchasing Power Parity (PPP)

The intuition behind PPP is straightforward: if a basket of groceries costs $100 in the United States and the equivalent basket costs 800 Mexican pesos, PPP implies the "fair" exchange rate is 8 pesos per dollar. The most famous shorthand is The Economist's Big Mac Index, which compares the local price of a McDonald's burger across countries to gauge whether currencies look overvalued or undervalued relative to PPP. It is a simplified illustration, not a trading signal.

PPP matters in market data for two main reasons. First, economists use PPP-adjusted GDP figures to compare living standards across countries more fairly than raw currency conversions allow — a dollar stretches further in a low-price economy. Second, PPP serves as a long-run anchor for what moves exchange rates: when a currency drifts far from its PPP value, economists note that historical forces — trade flows, inflation differentials, capital movements — have eventually pulled it back, though "eventually" can mean years or decades.

A critical confusion: PPP is a long-run concept, not a short-run predictor. Real exchange rates can deviate from PPP for extended periods because capital flows, interest-rate differentials, and risk sentiment dominate in the short run. PPP also assumes goods are freely tradable and identical, which is rarely true — haircuts and housing cannot be shipped across borders to arbitrage price differences. Country-level PPP data appears in the economic indicators section.