Peter Fimrite and Michael Cabanatuan

via San Francisco Chronicle

Human nature, as defined by those of us who use our morning runs to justify pigging out on jelly doughnuts, has a tendency to torpedo even high-minded goals — including, it turns out, fuel efficiency.

A study released Tuesday by economists at UC Davis, Yale, and MIT shows that families who own fuel-efficient cars tend to buy big, powerful gas guzzlers as their second vehicle, largely defeating the purpose of the little petrol sippers in their garages.

The researchers, who studied California Department of Motor Vehicle trends for two-car households over several years, likened the phenomena to the “diet soda effect,” in which people who buy diet drinks reward themselves by wolfing down greasy french fries.

“If people buy a more fuel-efficient car, down the road when they replace one of their cars, the car they buy is going to be less fuel-efficient,” said lead author David Rapson, an associate professor of economics at the UC Davis Department of Economics and co-director of the Davis Energy Economics Program. “So the effect of fuel economy standards is reduced.”

Not only that, Rapson said, but because of the fuel-cost savings, the owners of the fuel-efficient cars tend to drive them more, which ultimately leads to more gasoline being burned, thereby counteracting the decision not to drive the hulking sport utility vehicle.

These tendencies reduce by up to 60 percent the expected future gas savings from increased fuel economy in two-car households, said the study, which was funded by the California Air Resources Board. That’s the equivalent of saving 68 gallons a year compared with between 24 and 27 gallons, according to the study co-authored by James Archsmith of UC Davis, Kenneth Gillingham of Yale and Christopher Knittel of MIT.

“As someone who has dedicated his career to trying to figure out solutions to climate change, this is troubling,” Rapson said. It means “there is a strong force that we didn’t know about before that is going to erode the benefit of forcing people to buy more fuel-efficient cars.”

The results don’t mean humans are naturally greedy or hedonistic, Rapson said. In fact, …

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CEEPR Working Paper 2017-016