MIND THE GAP - THE VICIOUS CIRCLE OF MEASURING AUTOMOBILE FUEL USE

We review the circularity between estimates of automobile use, fuel co nsumption and fuel intensity. We find that major gaps exist between es timates of road gasoline, the quantity most often used to represent au tomobile fuel use in economic studies of transport fuel use, and the a ctual sales data of gasoline, diesel and other fuels used for automobi les. We note that significant uncertainties exist in values of both th e number of automobiles in use and the distance each is driven, which together yield total automobile use. We present our own calculations f or total automobile fuel use for a variety of OECD countries. We comme nt briefly on the impact of these gaps on econometric estimates of the price and income elasticities of automobile fuel use. We show that im proper use of the circularity often leads to gross errors in estimatin g fuel intensity and other indicators of energy use for personal trans port.