Aggregate energy analysis using an exogenous trend A two-state procedure was followed, involving a long-run cointegrating equation and a dynamic relationship in the form of an error correction model (ECM). The Granger representation theorem (Engle and Granger [9] ) states that if a set of I(1) variables are cointegrated (so that the resulting residual is stationary) then there is a valid error correction representation. A range of diagnostics were used to test the order of integration of the variables and it was concluded that logs of price and energy intensity could be considered I(1)