It's worse than that. From Wikipedia:
(Wikipedia)
"Historically, it is the sales-weighted average fuel economy, expressed in miles per gallon (mpg), of a manufacturer's fleet of current model year passenger cars or light trucks with a gross vehicle weight rating (GVWR) of 8,500 pounds (3,856 kg) or less, manufactured for sale in the United States. This system will change with the introduction of "Footprint" regulations for light trucks binding in 2011. Light trucks that exceed 8,500 lbs gross vehicle weight rating (GVWR) do not have to comply with CAFE standards; SUVs and passenger vans are exempt up to 10,000 lbs. In 1999, over half a million vehicles exceeded the GVWR and the CAFE standard did not apply to them.[2] In 2011, the standard will change to include many larger vehicles. "
The problem is not necessarily the existing CAFE standards for passenger vehicles per se, but the fact that the least efficient vehicles don't even fall under the standards we have!
Also, I've read recently that the powers that be are revisiting how fuel-efficiency for vehicles is measured in the first place. Apparently the existing standards use very, ahem, generous measures of a car's efficiency - not factoring in the realities of modern day driving patterns, for example (think lots of stop-and-go traffic, city-streets not highway, etc).