Saturday, October 31, 2009

Nominal and real exchange rates


  • The nominal exchange rate e is the price in foreign currency of one unit of a domestic currency.
  • The real exchange rate (RER) is defined as RER = e \left(\frac{P}{P^f} \right), where Pf is the foreign price level and P the domestic price level.

The RER is based on the GDP deflator measurement of the price level in the domestic and foreign countries (P,Pf), which is arbitrarily set equal to 1 in a given base year. Therefore, the level of the RER is arbitrarily set, depending on which year is chosen as the base year for the GDP deflator of two countries. The changes of the RER are instead informative on the evolution over time of the relative price of a unit of GDP in the foreign country in terms of GDP units of the domestic country. If all goods were freely tradable, and foreign and domestic residents purchased identical baskets of goods, purchasing power parity (PPP) would hold for the GDP deflators of the two countries, and the RER would be constant and equal to one.

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