How low can American drivers go?

In April, Americans drove fewer miles than last year. But the drop-off was much smaller than March's plunge.

Published June 19, 2008 5:29PM (EDT)

The New York Times tells us today what How the World Works has been obsessing on for months: "Driving Less, Americans Finally React to Sting of Gas Prices, a Study Says." The takeaway line: 2007 may end up being the peak year for gasoline consumption, ever, in the (past or future) history of the United States.

In the piece, Clifford Krauss also cites the latest report on American driving habits from the Department of Transportation: "Americans drove 1.8 percent fewer miles on public roads in April 2008 compared with the same month last year, the sixth consecutive month of driving mileage declines."

The stat piqued my curiosity, because the way the Department of Transportation has publicized the March 2008 numbers was by noting that Americans had driven 11 billion fewer miles this March than in March 2007. So, I wondered, what did a 1.8 percent decline in April represent, in terms of billions of miles traveled?

In April 2007, Americans drove 250.3 billion miles. In April 2008, Americans drove 245.9 billion miles. So this April, Americans drove only 4.4 billion fewer miles than they did last April, which is a pretty sharp reduction in the size of the overall reduction measured in March.

In April 2007, the drop-off from March 2007 added up to about 7 billion miles. But this year, Americans drove only 300 million miles less than they did in April.

What's the significance? Well, I've been repeatedly citing the March 2008 numbers as evidence that American demand for gas was not as "inelastic" as many had previously thought. Once the price of gas got high enough, we did end up changing our driving patterns. But the price of gas continued to rise in April, and Americans drove about the same number of miles, month to month. What that might suggest is that there are indeed limits to how much we can change our driving habits, before further improvements get increasingly difficult.

However, the really interesting numbers will arrive in another month, because when you review the numbers for previous years, there has historically been a huge month-to-month jump in May, compared to April. Last year, for example, Americans drove 16 billion more miles in May than they did in April. There may still be some room to cut the fat, in those numbers.

By Andrew Leonard

Andrew Leonard is a staff writer at Salon. On Twitter, @koxinga21.

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