Past financial crises have brought about declines in driving rates, but the sustained reduction in vehicle miles driven over the last 92 months, with no end in sight, is unprecedented. So what accounts for this trend? Plumer says that high gasoline prices are one factor, but "not the whole story."
"The other big part of the story is that young Americans are driving much, much less," he says. "Between 2001 and 2009, the average yearly number of miles driven by 16- to 34-year-olds dropped a staggering 23 percent."
"The Frontier Group has the most comprehensive look yet of why younger Americans are driving less. Public transportation use is up 40 percent per capita in this age group since 2001. Bicycling is up 24 percent overall in that time period. And this is true even for young Americans who are financially well off. Here are five big hypotheses: