Turkey, the UK , and Mexico (“undervalued by a whacking 55.9% against the greenback”) have gotten much cheaper over the past year.

The Big Mac index is built on the idea of purchasing-power parity, the theory that in the long run currencies will converge until the same amount of money buys the same amount of goods and services in every country. A Big Mac currently costs $5.06 in America but just 10.75 lira ($2.75) in Turkey, implying that the lira is undervalued. – Economist