"A burger isn't an exchange rate."
- A cheap burger can mean cheap labor, not a cheap currency. A Big Mac is mostly local wages and rent. Poorer countries pay less for both, so their burgers will look "undervalued" forever. That's why The Economist also publishes the adjusted version (section 2).
- Exchange rates don't follow burgers. Interest rates, trade and money flowing in and out move currencies much faster than prices catch up. Purchasing power parity is a long-run pull, not a forecast.
- Even The Economist calls it light-hearted. It started in 1986 as "burgernomics": a teaching tool, not a trading signal.
Even after adjusting for how rich each country is, most currencies still look cheap next to the dollar (section 2). The dollar is the world's reserve currency: people everywhere want it, and that demand props up its price. Whether that's strength or privilege depends on which side of the exchange you're on.