This paper provides new perspective on the poor performance of exchange rate models by focusing on the information structure of FX trading. I present a new theoretical model of FX trading that emphasizes the role of incomplete and heterogeneous information. The model shows how an equilibrium distribution of FX transaction prices and orders can arise at each point in time from the optimal trading decisions of dealers. This result motivates empirical investigation of how the equilibrium distribution of FX prices behaves using a new data set that details trading activity in the FX market. This analysis produces two striking results: (i) Much of the observed short-term volatility in exchange rates comes from sampling the heterogeneous trading decisions of dealers in an equilibrium distribution that, under normal market conditions, changes comparatively slowly. (ii) In contrast to the assumptions of traditional macro models, public news is rarely the predominant source of exchange rate movements over any horizon.
