An Odd Disparity

Why do British car purchasers buy vehicles that have a far higher average fuel economy than those in the US?

In 2009 (the last year that one can compare based on available statistics), the average new car fuel consumption for a gas-powered car was 43.6 miles per gallon (diesel vehicles actually pushes the fuel economy even higher). For the US, the new vehicle fuel efficiency for cars (which doesn't include SUVs) was 32.9.

That's a pretty big difference. Perhaps the difference is in the type of cars being purchased - the Brits are buying smaller vehicles than Americans and size directly correlates with fuel economy. It also goes to choice. Higher fuel economy is available for those who want it without the mandates - but people here in the US are by and large not interested in purchasing smaller cars.