The Adjusted Big Mac Methodology : A Clarification

The Economist's adjusted Big Mac index takes GDP into account in currency valuation, but the methodology is not explained. We show that the key to understanding the methodology is to distinguish between a currency's bilateral valuation (versus a specific currency) and the currency's overall valuation (versus a “basket” of a large number of currencies). Also, the adjusted Big Mac estimates of intrinsic FX rates have been better forecasts of actual FX changes than those of the original “raw” Big Mac index