Nate Silver crunches the numbers:

I built a regression model that accounts for both gas prices and the unemployment rate in a given month and attempts to predict from this data how much the typical American will drive. The model also accounts for the gradual increase in driving over time, as well as the seasonality of driving levels, which are much higher during the summer than during the winter... The model predicts that given a somewhat higher unemployment rate but much lower gas prices, the lower gas prices should have won out: Americans should have driven slightly more in January 2009 than they had a year earlier. But instead, as we've described, they drove somewhat less. In fact, they drove about 8 percent less than the model predicted.

If you got caught up in the mathematical jargon, it's as simple as this: gasoline prices became so cheap after last summer that we should have taken advantage of them and driven more than ever. The fact that we didn't tells us something important. If you click through to Silver's article you will see a graph that looks like it would be useful if Esquire didn't try to make it look really slick and 3-D like.

What will be really interesting is to see how this plays out over the summer when gasoline is seasonally most expensive and driving is at its seasonal high. If the model holds, then we might actually be on to something..