Last August the Obama administration announced new fuel economy standards. Cars and trucks sold in the United States must reach an average fuel economy of 41.7 miles per gallon by 2020, increasing to 54.5 miles per gallon by 2025. Supporters of the tightened standards argue that they will reduce oil consumption by billions of barrels.
These standards will make cars smaller, lighter, and more fuel-efficient. Will this limit the choices available for consumers? Yes and no. It is going to become more difficult to buy new trucks, SUVs, and minivans. However, because fuel economy standards affect new vehicles only, these larger, fuel-inefficient vehicles are going to continue to be a substantial part of the U.S. vehicle fleet for many years.
Mark Jacobsen (UCSD) and Arthur van Benthem (University of Pennsylvania) are looking closely at the market for used cars and trucks and finding that vehicle scrappage is extremely important. Their complete study will be available soon. In the meantime, they shared with me this figure which shows annual scrap rates by MPG quartile.
As you would expect, older vehicles are scrapped at much higher rates. But what is particularly interesting is the comparison across MPG quartiles. Among vehicles 9+ years old, the least efficient vehicles (Quartile 1) have the lowest scrappage rates, remaining in the vehicle stock long after the smaller, fuel-efficient vehicles (Quartile 4) have been sent to the scrapyard.
Jacobsen and van Benthem find that new fuel economy standards will exacerbate this pattern, leading fuel inefficient vehicles to remain in the vehicle stock even longer. The reason is that tightened fuel economy regulation leads to higher prices for large and fuel-inefficient new vehicles. More people will buy a used SUV or pickup truck instead of a new one. This means that prices of used vehicles increase, giving owners an incentive to postpone the decision to scrap their vehicles. In economics this is known as the Gruenspecht effect, named after a study by Howard Gruenspecht. The original study is available here.
Overall, Jacobsen and van Benthem find that increases in fuel consumption by fuel inefficient used cars will offset about 1/5th of the direct impact of updated fuel economy standards. This Gruenspecht effect is one of the reasons why 92% of economists would prefer a gasoline tax over fuel economy standards. (According to a new study available here, only 22% of non-economists feel the same way.) Whereas standards treat new and used cars differently, a gas tax does not. And a gas tax both encourages consumers to buy more fuel efficient vehicles and encourages them to drive them less.