apples and oranges and gas prices

AAA announced that Virginia families will spend $246 more on gas this summer. OK, fine. How did they get this amount? It appears that AAA assumed that each vehicle gets 20 mpg and that everyone will drive the same amount as last summer. They compared this summer’s average gas price of $3.89 to last summer’s gas prices.

My main problems with this:


  • Average fuel economy (mpg) increases every year. In 2006, the average car and truck had fuel economies of 22.4 mpg and 18 mpg (up from 22.1 mpg and 17.7 mpg in 2005). (From BTS).

  • With gas prices this high, people will drive less. In 2006, the average car traveled 12K miles, compared to 12.1K miles in 2005 and 12.5K miles in 2004 (From BTS).

  • Families will likely all pile into a Honda Civic for a family trip rather than the Ford Excursion, so even when families are driving, they may be driving a more fuel-efficient car.

  • Gas prices are not static. Gas prices typically increase from Memorial Day to Labor Day each year, and I’m not sure that they increase at the same rate year to year since they are a function of several key outside factors.

Comparing apples to apples is ideal, but in the case of fuel consumption, there is a definite system effect. People are changing their driving habits, so comparison to old driving habits is very difficult. Sometimes comparing apples to oranges is the best thing to do. I couldn’t find a AAA report out there, so maybe they did a more rigorous analysis, but I’m not holding my breath.

6/5 Update: No sooner did I write this that I read that Americans are indeed driving less. The US Federal Highway Administration reported that Americans drove 4.3% less in March 2008 than they did in March 2007 (about 11 billion fewer miles total).

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