Purchasing Power Parity: A Time Series Analysis of the U.S. and Mexico, 1995–2007

This paper presents indirect evidence that absolute purchasing power parity (PPP) may hold in the long-run between Mexico and the U.S., but due to data limitations, the relationship could not be tested directly. Thus it is not clear if absolute PPP holds in the long run between the U.S. and Mexico. Given that relative PPP is a necessary, but not sufficient, condition for absolute PPP to hold, this study tests the relationship between the change in the log of the exchange rate, and the changes in the log of the U.S. producer price index (PPI) and the Mexican PPI. Here, the absence of relative PPP would indicate that absolute PPP could not hold. Given that all the relevant variables in first difference log are stationary, PPP in its relative form holds and OLS can be applied directly in a VAR model setting, viz., treating all variables initially as potentially endogenous. The estimates indicate one-way Granger causality from the percentage change in the exchange rate to the percentage change in the Mexican price level, which is not an implausible result for an emerging nation such as Mexico which imports a significant fraction of (dollar denominated) intermediate products and capital inputs.