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The Big Mac Index was introduced in The Economist in September 1986 by Pam Woodall as a semi-humorous illustration and has been published by that paper annually since then.The index also gave rise to the word burgernomics.
UBS Wealth Management Research has expanded the idea of the Big Mac Index to include the amount of time that an average worker in a given country must work to earn enough to buy a Big Mac.The working time-based Big Mac index might give a more realistic view of the purchasing power of the average worker,as it takes into account more factors,such as local wages.
One suggested method of predicting exchange rate movements is that the rate between two currencies should naturally adjust so that a sample basket of goods and services should cost the same in both currencies (PPP).In the Big Mac Index,the "basket" in question is considered to be a single Big Mac burger as sold by the McDonald's fast food restaurant chain.The Big Mac was chosen because it is available to a common specification in many countries around the world,with local McDonald's franchisees having significant responsibility for negotiating input prices.For these reasons,the index enables a comparison between many countries' currencies.
The Big Mac PPP exchange rate between two countries is obtained by dividing the price of a Big Mac in one country (in its currency) by the price of a Big Mac in another country (in its currency).This value is then compared with the actual exchange rate; if it is lower,then the first currency is under-valued (according to PPP theory) compared with the second,and conversely,if it is higher,then the first currency is over-valued.