It's pretty shocking to see that between 1968 and 2004, the miles driven by Americans doubled. It's also nice to see things moving back to the left. Do Americans realize that, no matter how nicely appointed their autos, the quality of life while driving is a miserable fraction of that spent out in "the real world"?
All other things being equal, economic theory predicts that instead of such a loopy curve, we'd see a straight slope up from left to right. Of course, this isn't the whole story. To see the entire economic picture, we'd also have to see a supply curve of gasoline produced in the US market for the same period of time. Perhaps also an efficiency curve of average MPG for autos in the US market. Perhaps looking at such a 3- or 4-dimensional graphic would give me a headache!