Econometric methods and purchasing power parity: short- and long-run PPP

This paper defines the different versions of the purchasing power parity and establishes the existing relationships between them in the light of econometric techniques. Monthly and annual data for real exchange rates are studied through a variance ratio test. Unlike other authors, it is found that there is not explosive behaviour in the real exchange rate when monthly data are used. Besides, stationarity is easily accepted using annual data. These results allow to reconcile the two main versions of the purchasing power parity and also explain why trade imbalances are persistent but not permanent.