Effective Exchange Rate
The effective exchange rate is an index that measures the value of a currency against a basket of other currencies, weighted according to the importance of each trading partner. Unlike a bilateral exchange rate, which compares two currencies, the effective exchange rate summarises the overall external value of a currency and is therefore a better indicator of a country's international competitiveness. Nominal and real versions of the index are used, and the real effective exchange rate, which adjusts for relative prices, is a key variable in the analysis of trade and external balance.
Nominal versus real
The nominal effective exchange rate is a weighted average of bilateral nominal exchange rates, expressed as an index relative to a base period. The weights reflect the shares of each trading partner in the country's trade, so that currencies of important partners have a larger influence on the index. A rise in the index means the currency has appreciated on average against its trading partners, while a fall means it has depreciated.
The real effective exchange rate adjusts the nominal index for differences in prices or costs between the home country and its trading partners. It is typically computed using relative consumer prices, unit labour costs, or producer prices. Because it measures the relative price of domestic goods in international markets, the real effective exchange rate is the more relevant indicator of competitiveness: a rise means domestic goods have become more expensive relative to foreign goods, while a fall means they have become cheaper.
Construction and weighting
Constructing an effective exchange rate index requires a set of bilateral exchange rates, a set of weights, and a base period. Weights may be based on bilateral trade shares, on trade with all partners, or on more sophisticated measures that account for competition in third markets and for the composition of trade. Different institutions publish indices with different weights and price measures, so the level and the movements of the indices can differ.
The choice of price measure matters. Indices based on consumer prices reflect broad cost developments, while indices based on unit labour costs focus on the cost of labour per unit of output, and indices based on export prices focus on the prices of traded goods. Because the measures capture different concepts, they can give different signals about competitiveness, and analysts often examine several indices together to reach a robust conclusion.
Uses
The effective exchange rate is used to assess the external position of an economy and to analyse the effects of exchange rate movements on trade. An appreciation of the real effective exchange rate makes exports more expensive and imports cheaper, tending to worsen the trade balance, while a depreciation does the opposite. Because these effects operate with lags, and because they can be offset by changes in demand and productivity, the relationship between the effective exchange rate and the trade balance is not mechanical.
The index is also used to estimate the degree of exchange rate misalignment. By comparing the actual real effective exchange rate with an estimated equilibrium level, analysts can assess whether a currency is overvalued or undervalued. Such assessments inform surveillance by international institutions, the design of exchange rate policy, and the analysis of the sustainability of external positions.
Limitations
The effective exchange rate has limitations. Aggregation into a single index conceals the fact that a currency may move in different directions against different partners, and the choice of weights affects the results. The basket may not capture competition from countries that are not major trading partners but that compete in export markets. Changes in the composition of trade over time require the weights to be updated, and stale weights can distort the index.
The index also abstracts from other determinants of competitiveness, such as productivity, quality, and the availability of inputs. A depreciation of the real effective exchange rate does not automatically improve competitiveness if domestic inflation rises, and an appreciation does not necessarily harm it if productivity is growing faster than abroad. The index is therefore best used as one input among several in the analysis of external performance, rather than as a complete measure of competitiveness.
Relationship with the terms of trade
The real effective exchange rate is closely related to the terms of trade, the ratio of export prices to import prices. A depreciation of the real effective exchange rate, which lowers the relative price of domestic goods, tends to improve the terms of trade measured in volume terms only if the volume of exports rises sufficiently. The interaction between prices and volumes, governed by elasticities, determines whether a depreciation improves or worsens the trade balance, a relationship summarised in the Marshall-Lerner condition.
Movements in the real effective exchange rate also reflect changes in productivity and in the composition of trade. An economy whose productivity grows faster than its trading partners may experience an appreciation of its real effective exchange rate as a consequence, without any loss of competitiveness, because its goods are produced more efficiently. The index must therefore be interpreted alongside measures of productivity and cost to draw conclusions about competitiveness.
Policy and surveillance
The effective exchange rate is a central input to international surveillance of exchange rate and external balance policies. Institutions assess whether currencies are misaligned relative to fundamentals, and they use estimates of the equilibrium real effective exchange rate as a benchmark. Such assessments inform recommendations about exchange rate policy, about the pace of adjustment, and about the need for structural reforms to improve competitiveness.
The index is also used in the design of exchange rate regimes. Countries that peg to a basket of currencies use a basket that resembles an effective exchange rate, stabilising the average external value of their currency rather than its value against a single partner. The choice of weights and of the anchor currencies reflects the pattern of trade and the objectives of policy, and it affects how external shocks are transmitted to the domestic economy.
Data and institutions
Several institutions publish effective exchange rate indices, with differences in coverage, weighting, and price measures. Some use broad baskets of many partners, while others focus on a smaller set. Some adjust for third-market competition, recognising that exporters compete not only at home but also in foreign markets. The availability of these indices, and of the underlying data, facilitates analysis by researchers and policymakers.
The choice among indices matters for empirical work. Results can be sensitive to the measure used, and analysts often test the robustness of their conclusions across several indices. Improvements in data, including more granular trade statistics and better measures of services trade, are gradually improving the accuracy of the indices, and continued attention to measurement is important for the quality of exchange rate analysis.