Auto sales have enjoyed their best year since 2007, but... Auto sales have enjoyed their best year since 2007, but carmakers face some daunting longer-term trends. (AP photo).
Don't own a car? You're not alone. The percentage of zero-car families is increasing in the United States.

In a brief released earlier this week, researchers said there has been an uptick in the share of American households that do not own an automobile. It's the first time in 50 years they've recorded an increase.

Starting in 1960, the share of American families without a car steadily declined until reaching an all-time low of 8.7 percent in 2007. By 2011, the latest year for which data is available, the share had risen to 9.3 percent.

At first glance, it would appear the rise would be related to the economic impact of the Great Recession. But the study's authors at the American Association of State Highway and Transportation Officials say that's not the only factor behind the trend.

"Changes in alternatives to travel, such as communication substituting for travel and renewed interest in and availability of options such as transit, bike and walk, helped dampen interest in expanding auto ownership," they wrote.

That underscores previous work that points to a fundamental shift in how Americans move around.

Earlier this year, the Federal Highway Administration released data that showed the number of vehicle miles traveled (VMT) peaked in the U.S. in 2004, and has since declined for eight consecutive years.

Although the total number of vehicle miles traveled has increased slightly due to population growth, the number of VMT per capita declined by 0.4 percent in 2012, about 37 miles per person over the previous year.

There have been other studies this year that have documented a generational shift in attitudes of millenials and Generation Y away from cars – they are more inclined to view them as a financial burden.

At the same time, cars may be more affordable. In another note in the AASHTO study, authors, who culled data from the American Community Survey in the U.S. Census, note that vehicles have become better built and thus "can be amortized over longer periods."

In August, automotive research firm Polk said the average car on the road was 11.4 years old, an all-time high. Polk forecasters said consumers desire to avoid a monthly payment combined with the better durability of vehicles to contribute to the trend.

AASHTO says this has been "one of the most significant, and least recognized, technological changes in transportation over the past 50 years."

Pete Bigelow is an associate editor at AOL Autos. He can be reached via email at and followed on Twitter @PeterCBigelow.

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