Abstract Shifts among economic sectors within manufacturing have had significant effects on industrial energy demand since 1973. At least one-third of the reduction in U.S. energy intensity for fossil fuels can be attributed to sectoral shifts over this historical period. Shifts among economic sectors will continue to be an important source of uncertainty in forecasting industrial energy demand. Without greater consensus on the major causes of these shifts, analysts will be unable to separate how much of the past shifts can be reversed with changed energy and economic conditions and how much will remain embedded in the economic structure. Standard economic projections anticipate a continuation of the shift away from large industrial energy-using sectors, although at a slower rate. The Wharton economic projections used recently in an Energy Modeling Forum (EMF) study indicated a decline rate of about half that experienced during the 1973–1981 period. Even so, this effect alone could contribute as much as 0.5% per annum to the rate of decline in aggregate energy intensity within manufacturing.