Ever since 2007, when oil prices start spiking, Americans as a whole have been driving less. A lot less. But is this just a temporary blip—due mainly to the recession and gas prices that pal around with $4 per gallon signs now and again? Or have driving patterns in the United States undergone some new, permanent shift? Earlier today, Jared Bernstein posted a graph from the Federal Highway Administration and raised the question:

Notice that, in previous recessions, driving barely budged at all. After 2007, by contrast, vehicle-miles traveled took a big nosedive and never recovered. Of course, one difference is that this time around, oil prices are still high. And, despite presidential candidate Rep. Michele Bachmann’s pledge to bring gas below $2 per gallon, most analysts think that strong demand from developing countries will prevent oil prices from plunging back to the rock-bottom levels we saw in the 1990s. It’s possible that U.S. drivers are simply adjusting to this new normal.

There’s also a theory floating around that Americans—especially young Americans—are simply no longer as car crazy as they were in the 1970s. In 1976, three-quarters of all 17-year-olds had drivers’ licenses. By 2008, that was down to 49 percent. Last year, Zipcar, the car-sharing company, did a survey that found that 67 percent of 25- to 34-year-olds would prefer to drive less, especially if alternatives were available. (Mind you, Zipcar is hardly a disinterested party here, but other surveys have yielded similar results.)

What could explain this cultural shift? Maybe more young people are worried about the price of gas or the environment. But—and this is just a theory—technology could play a role, too. Once upon a time, newly licensed teens would pile all their friends into their new car and drive around aimlessly. For young suburban Americans, it was practically a rite of passage. Nowadays, however, teens can socialize via Facebook or texting instead—in the Zipcar survey, more than half of all young adults said they’d rather chat online than drive to meet their friends.

But that’s all just speculation at this point. As Bernstein says, it’s still unclear whether the decline in driving is a structural change or just a cyclical shift that will disappear once (if) the U.S. economy starts growing again.