There are several problems associated with forecasting exchange rates using single- equation econometric models, including: O they explain the value of the exchange rate in terms of other variables, without explaining how these other variables are determined they explain the value of the exchange rate in terms of other variables, without explaining how these other variables are determined AND they may be conditional on the future value of the explanatory variables they may be conditional on the future value of the explanatory variables they are very expensive models to run