There has been growing speculation over the past decade about the hypothesis that the share of national income that is spent on energy is a significant macroeconomic factor, and that countries tend to gravitate back towards a relatively narrow range of energy expenditure.  This report presents the most extensive database yet developed to examine this question, and suggests indeed that national energy expenditures across market economies have tended to be in the range 8+/-2%, and that expenditures outside this range lead to reactions which bring it back, though with time lags measured in decades for energy systems to fully react.  We argue that this has significant policy implications”