Big Mac Index

International Economics Foreign Exchange
The Big Mac Index is an informal purchasing-power-parity comparison that uses the price of a Big Mac across countries to illustrate currency misalignment.
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The Big Mac Index is an informal purchasing-power-parity comparison that uses the local price of a Big Mac to show whether a currency looks overvalued or undervalued relative to another.

Core idea

Purchasing power parity says that, in the long run, exchange rates should move toward levels that equalize prices of comparable baskets across countries. The Big Mac Index turns that abstract idea into a simple rule of thumb by using one standardized product.

If:

  • a Big Mac costs 5 dollars in the United States, and
  • the same burger costs 30 units of another currency abroad,

then the implied PPP exchange rate is 6 foreign-currency units per dollar. If the actual exchange rate is very different, the currency may look under- or overvalued relative to this benchmark.

Why economists still use it

The index is intentionally simplified, but it is useful pedagogically because it shows:

  • how PPP works,
  • why exchange rates can deviate from goods prices,
  • why non-traded costs such as rent and wages matter.

It is not a precise valuation model. It is a teaching device and a rough indicator.

Knowledge Check

### What theory does the Big Mac Index illustrate? - [x] Purchasing power parity - [ ] Comparative advantage - [ ] Quantity theory of money - [ ] Rational expectations > **Explanation:** The index is a simplified PPP comparison based on the price of a standardized product across countries. ### Why can the Big Mac Index differ from the actual exchange rate? - [x] Because transport costs, taxes, wages, rents, and market structure differ across countries - [ ] Because burger prices have no relation to currencies at all - [ ] Because PPP says all prices must be identical every day - [ ] Because exchange rates are fixed by law in every country > **Explanation:** PPP is a long-run benchmark, not a statement that all cross-country prices line up perfectly in the short run. ### Is the Big Mac Index a full model of currency valuation? - [ ] Yes - [x] No - [ ] Yes, because one product captures every macroeconomic variable - [ ] No, because exchange rates never respond to prices > **Explanation:** It is intentionally simple and useful as an illustration, not as a complete model of exchange-rate determination.
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