Included currencies
Based on nominal exchange ratesThe index is computed as the geometric mean of the bilateral exchange rates of the included currencies. The weight assigned to the value of each currency in the calculation is based on trade data, and is updated annually (the value of the index itself is updated much more frequently than the weightings).[1] The index value at time t is given by the formula:[1]
where
Based on real exchange ratesIn order to account for countries whose currencies experience differing rates of inflation from that of the United States the real exchange rate is a more informative measure of the dollar's worth. This is compensated for by adjusting the exchange rates in the formula using the consumer price index of the respective countries. In this more general case the index value is given by:[1]
where
Source : Federal Reserve Bulletin |
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