Bryan Christie Design

This is surely one of the signs of the apocalypse: Americans aren't driving as much as they used to.

In January, according to statistics compiled by the Federal Highway Administration, Americans drove a collective 222 billion miles. That's a lot of time spent behind the wheel — enough to make roughly eight hundred round-trips to Mars. It translates to about 727 miles traveled for every man, woman, and child in the country. But that figure was down about 4 percent from January 2008, when Americans averaged 757 miles of car travel per person. And this was no aberration: January 2009 was the fifteenth consecutive month in which the average American drove less than he had a year earlier.

This is, historically speaking, highly unusual behavior. If there have been two seemingly immutable trends for the American consumer, they're that he's eaten more every year and driven more every year. The late 1960s are sometimes assumed to be the height of car culture. But in January 1970, the average American drove only about 393 miles in his vehicle, or about half of what he drove every month until recently.

The one thing that has sometimes caused Americans to put on the brakes is higher gas prices. Although driving is a relatively inelastic activity — a doubling of gas prices reduces miles traveled by only a small fraction — it has nevertheless been somewhat sensitive to changes in fuel costs. Vehicle miles traveled fell between 1981 and 1982, for instance, when the price of gas was the equivalent of three dollars in today's prices, and between 1990 and 1991, when the Persian Gulf war triggered a temporary spike in the price at the pump.

Gas prices, of course, were exceedingly high last summer, peaking at $4.06 a gallon in July 2008; it isn't surprising that Americans were driving less then. But prices have since fallen by more than half, and Americans have yet to pick up the pace on the roads.

How much of it is just a result of the bad economy? The unemployment rate has soared significantly since last summer; perhaps the only good thing about losing your job is that you no longer have to endure the drive to work.

To sort this out, 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 results of the model are shown for the month of January in each year since 1980 in the graph above.)

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.

Could it be that there's been some sort of paradigm shift in Americans' attitudes toward their cars? Perhaps, given the exorbitant gas prices of last summer, Americans realized that they weren't quite as dependent on their vehicles as they once thought they were.

For people like me who live in big cities where one does not need a vehicle to get by, there is a certain romantic attraction to this story. Why, if only all those Bubbas could ditch their SUVs, take the monorail to work, and buy their families a bunch of Schwinns, life would be just grand!

In the real world, of course — outside perhaps a half dozen major metropolitan areas — American society has been built around the automobile. Although the consumer can make some adjustments in response to changes in fuel prices more or less immediately — for instance, popping in a DVD rather than driving to the movies — others take more time. If a commuter living in the suburbs were to decide he wanted to be closer to the city because of fuel costs, it would still take him many months to sell his house (especially in this market), pack his bags, and find a new school for his kids.

There is strong statistical evidence, in fact, that Americans respond rather slowly to changes in fuel prices. The cost of gas twelve months ago, for example, has historically been a much better predictor of driving behavior than the cost of gas today. In the energy crisis of the early 1980s, for instance, the price of gas peaked in March 1981, but driving did not bottom out until a year later.

Thus, the continued decrease in driving today reflects, in part, a delayed reaction to hundred-dollar-a-barrel oil. Maybe our commuter finally did get fed up and move his family to the city, but it took him until now to do so. The real test will come as the summer unfolds and Americans have had time to get "used to" lower gas prices.

Still, there is some evidence that more Americans are at least entertaining the idea of leading a more car-free existence. Between October 2004, when gas prices first hit two dollars a gallon, and December 2008, when they fell below this threshold, three cities with among the largest declines in housing prices were Las Vegas (-37 percent), Detroit (-34 percent), and Phoenix (-15 percent), each highly car-dependent cities. Conversely, the two markets with the largest gains in housing prices were Portland, Oregon (+19 percent), and Seattle (+18 percent), communities that are more friendly to alternate modes of transportation.

The exceptionally sluggish pace of new-vehicle sales, moreover, in the face of extremely attractive incentives being offered by the automakers might imply that Americans are considering making more-permanent adjustments to their lifestyles. And the denigration of the brand of the Big Three automakers in light of their financial difficulties — about one third of Americans have generally told pollsters they will buy only an American-made car — might reduce some of the patriotic associations with the activity of driving. Building a light-rail system might not persuade Bubba to get rid of his vehicle — but forcing him to buy foreign might.

Nate Silver runs the political Web site FiveThirtyEight.com and is an analyst and writer for Baseball Prospectus.

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