In the ’80s, the average car in the US got about 23 miles per gallon (mpg). Technological advances since then should mean that they get around 37mpg, but the average is still only 27mpg.

Writing in the American Economic Review, Christopher Knittel says that between 1980 and 2006, American cars became much heavier and more powerful. The average car’s weight went up by 26% and its horsepower increased by 107%.

Since transport in the US is responsible for over 30% of the country’s greenhouse gas emissions, increased mileage would be much better for the environment.

Petrol prices in the US have been very low for a long time, so Knittel says it’s understandable why drivers want big, powerful cars, as they’re cheap to run.

He says that manufacturers need to make cars the size and power they were in the ’80s, but with modern fuel efficient technology. If that were to happen, Knittel says that 52mpg could be possible by 2020.