… if we today were driving cars of the same size and power that were typical in 1980, concludes a new study by MIT economist Christopher Knittel. Of course, the Obama administration has set new corporate average fuel economy standards at 35.5 mpg for 2016. MIT News summarizes Knittel's findings:
Contrary to common perception, the major automakers have produced large increases in fuel efficiency through better technology in recent decades. There's just one catch: All those advances have barely increased the mileage per gallon that autos actually achieve on the road.
So what happened to the missing gas mileage?
…between 1980 and 2006, the average gas mileage of vehicles sold in the United States increased by slightly more than 15 percent — a relatively modest improvement. But during that time, Knittel has found, the average curb weight of those vehicles increased 26 percent, while their horsepower rose 107 percent. All factors being equal, fuel economy actually increased by 60 percent between 1980 and 2006, as Knittel shows in a new research paper, "Automobiles on Steroids," just published in the American Economic Review (download PDF).
Thus if Americans today were driving cars of the same size and power that were typical in 1980, the country's fleet of autos would have jumped from an average of about 23 miles per gallon (mpg) to roughly 37 mpg, well above the current average of around 27 mpg. Instead, Knittel says, "Most of that technological progress has gone into [compensating for] weight and horsepower."
This seems an example of the energy rebound effect in which increased energy efficiency encourages people to use even more energy; in this case to fuel bigger and peppier cars.