Mind the gap The vicious circle of measuring automobile fuel use

We review the circularity between estimates of automobile use, fuel consumption and fuel intensity. We find that major gaps exist between estimates of road gasoline, the quantity most often used to represent automobile fuel use in economic studies of transport fuel use, and the actual sales data of gasoline, diesel and other fuels used for automobiles. We note that significant uncertainties exist in values of both the number of automobiles in use and the distance each is driven, which together yield total automobile use. We present our own calculations for total automobile fuel use for a variety of OECD countries. We comment briefly on the impact of these gaps on econometric estimates of the price and income elasticities of automobile fuel use. We show that improper use of the circularity often leads to gross errors in estimating fuel intensity and other indicators of energy use for personal transport.