However, wanting higher mileage cars and buying them are two different things. American car-buyers seem to have a schizophrenic (and please don't bother to explain what schizophrenia really is because I know, I'm just using the word to make a point that people will understand) attitude. They want big, imposing cars and trucks with lots of power and high mileage, with the former taking priority. They don't seem to be willing to go with smaller, less powerful vehicles to get efficiency. This is of course a generalization since many people do buy smaller cars, but the majority still go big. So there just isn't enough demand (at least until gas prices go significantly higher) to support a larger supply of high mileage cars.
Another major issue in the drop in high mileage car availability is the temporary absence of the many of the diesel models that were previously available. This is of course due to changes in diesel emissions rules. The new engines that meet the new standards are becoming available in 2007, and more will be in the future. Over the next few years many more diesel vehicles will be available in the US along with plug-in hybrids and EVs. This should help to reverse the trend. Nonetheless, until American drivers start putting their money where their mouths are on mileage, it can only go so far.