A handful of currencies, especially the US dollar, play a dominant role in international trade. We survey the active theoretical and empirical literature that documents patterns of currency use in global trade, the implications of dominant currencies for international transmission of shocks,...

The real exchange rate (RER) measures relative price levels across countries, capturing deviations from purchasing power parity (PPP). RER is a key variable in international macroeconomic models as it is central to equilibrium conditions in both goods and asset markets. It is also one of the...