they do? then I am mistaken and apologize. I remember reading something last year saying that a bill requiring stricter regulation of fuel economy did not pass. I was under the impression that they had no set requirements, hence the wide range in fuel economy rates. some are as low as 8mpg, some as good as 25mpg. I would think that requiring a higher minimum (15MPG, for instance) would be a good idea, thats all.
Nope, there are two CAFE standards. One for passenger cars and the other for 'light trucks'. An SUV is a light truck. There was an attempt to raise the CAFE standards for light trucks last year that failed.
CAFE works by limiting the size and weight of the vehicle. (Sorry, there's no engineering way around that fact.) The only way to significantly increased gas mileage is decreased weight. Well, you can make the engine and transmission more efficient but there are costs associated with that as well.
The funny thing is, there were cars available that got very high mileage before CAFE was passed. They were unpopular and lots of folks chose to drive large less efficient vehicles. There are always 'do-gooders' who would force you to do the 'right thing' and are willing to limit your freedom of choice in order to do so. CAFE is a perfect example of that type of thinking.