Economisthas link after link devoted to a discussion of the Big Mac Index:
Burgernomics is based on the theory of purchasing-power parity, the notion that a dollar should buy the same amount in all countries. Thus in the long run, the exchange rate between two countries should move towards the rate that equalises the prices of an identical basket of goods and services in each country. Our “basket” is a McDonald’s Big Mac, which is produced in about 120 countries. The Big Mac PPP is the exchange rate that would mean hamburgers cost the same in America as abroad. Comparing actual exchange rates with PPPs indicates whether a currency is under- or overvalued.
This is a rather amusing variation on PPP, although one would presume that the price of a burger would vary somewhat based on the proximity to cheap beef. One also wonders about gauging the economy of India.
(Hat tip: Steven Taylor)