The Big Mac Index dashboard on this site is a daily-nowcast extension of The Economist's Big Mac Index. The Economist publishes the underlying local-currency prices twice a year (January and July); we hold those prices fixed between releases and recompute the USD-implied price every morning against the previous day's European Central Bank FX rates.
This page documents the formula, refresh cadence, sources, and limitations. The Big Mac Index is a deliberate simplification of purchasing-power parity — we lean into the simplification and try to be honest about where it breaks down.
Formula
For each country and each calendar day, we compute two numbers:
Implied USD price — what a local Big Mac would cost in dollars if you converted today at the European Central Bank's reference rate:
implied_usd_price = local_price ÷ fx_today
where local_price is The Economist's published local-currency price for the most recent release, and fx_today is the units of that currency per US dollar from the latest ECB rate via Frankfurter.
Overvaluation — how far the implied USD price sits above or below the USA Big Mac price for the same release:
overvaluation = (implied_usd_price ÷ usa_release_price) − 1
A positive number means the local currency is overvalued relative to the dollar by the Big Mac standard; a negative number means undervalued.
Worked example — Euro area, January 2026 release
- Local price: €6.08 (Economist Jan 2026 release).
- Today's FX: €0.8536 per USD (ECB via Frankfurter).
- Implied USD price = €6.08 ÷ 0.8536 = $7.12.
- USA release price: $6.12.
- Overvaluation = ($7.12 ÷ $6.12) − 1 = +16.4%.
The euro is overvalued against the dollar by roughly 16% on this measure today, given the same local Big Mac price as in January.
Refresh cadence
- 06:00 UTC daily — pull the latest Big Mac CSV from TheEconomist/big-mac-data, recompute the FX nowcast against the most recent FX file, write
big-mac.json, mirror to the theme, redeploy. - 17:00 UTC daily — pull yesterday's ECB reference rates from Frankfurter, backfill currencies the ECB doesn't publish (ARS, EGP, TRY, VND, etc.) from ExchangeRate-API's free tier, write
fx-rates.json. - Twice a year (Jan + Jul) — The Economist publishes a new release with refreshed local-currency Big Mac prices. Our daily script detects the new tag, re-pulls the CSV, and rebases the nowcast.
Page-generation, FX-rate, and release timestamps are surfaced as a transparency strip at the top of the dashboard.
Sources
- Big Mac prices — The Economist Big Mac Index, distributed under CC BY 4.0. 55+ countries (and the Euro area), 1986 → present. Released biannually.
- FX rates (primary) — European Central Bank daily reference rates, served via Frankfurter. Working-day cadence (no weekend update).
- FX rates (fallback) — ExchangeRate-API free tier, for currencies the ECB doesn't publish (Argentine peso, Egyptian pound, Turkish lira, Vietnamese đồng, several others).
- Country boundaries — Natural Earth 110m countries, in the public domain.
Limitations
The Big Mac Index is a one-good basket. A handful of caveats matter when reading our nowcast:
- Stale local prices. Between Economist releases the local-currency price doesn't move. Real Big Mac prices drift with menu changes, local inflation, and franchise pricing decisions; our number won't reflect that drift until the next release. In low-inflation economies this is a small effect; in high-inflation economies it isn't.
- Hyperinflation. We flag countries whose currency is in known high-inflation territory (Argentina, Turkey, Lebanon, Venezuela, Sudan, Zimbabwe). For these, the implied USD price drifts noticeably as FX moves while the menu price stays fixed in our data; treat the headline number with caution.
- FX freshness. ECB publishes weekdays only. Saturday and Sunday show Friday's rate. Holiday closures (Easter, Christmas, May Day) carry the prior business day's rate forward.
- It's a Big Mac, not a basket. The Big Mac is one good — beef-and-bun calories, with rent, labour, and tax baked in. It correlates with broader purchasing-power-parity measures (we'll layer those in via World Bank ICP in Phase 5) but it isn't itself one. A country can be expensive for Big Macs and cheap for housing, or vice versa.
- Coverage. Roughly 55 countries plus the Euro area. Countries not in The Economist's dataset show as grey on the map; this is the source's coverage, not a curatorial choice.
- The Euro area is treated as one country. The Economist publishes one price for the Eurozone as a whole. Country-level variation within the Eurozone (a Big Mac in Estonia vs. one in France) isn't reflected.
License & attribution
This dashboard is built on The Economist's Big Mac Index dataset, which is published under CC BY 4.0. Our derived dataset (the nowcast, history, sparkline data) inherits that license.
If you cite our numbers, please credit both The Economist (for the underlying index) and onesandwich.com (for the FX nowcast). The code, schemas, and refresh scripts live in github.com/lekashman/onesandwich.