ECONOMICS: The MPG Illusion, by Richard P. Larrick and Jack B. Soil. Science, 20 June 2008, V320, N5883, pp 1593-1594 (podcast here)

The authors here suggest that we turn MPG upside down and look instead at GPM. Miles per gallon is the most common way of expressing fuel efficiency in the United States but it is an incomplete picture. Looking at gallons per mile or gallons per 100 miles gives a better indication of costs and savings. Doing the math here we find that the best public policy would be to remove or improve the most inefficient vehicles rather than trying to improve the efficiency of already “efficient” vehicles. The data reported in this article shows that changing the way these terms are used does affect behavior.