SOUTHFIELD — The average age of cars and light trucks currently in operation in the U.S. has increased to 10.8 years, according to Polk. Passenger cars showed a modest increase in age since 2010, edging up from 11 years to just 11.1 years at the end of June 2011. Light trucks, including pickups and SUVs, showed a more sizeable gain in the same timeframe, inching up from 10.1 years to 10.4 years.

Average vehicle age overall has been increasing quickly over the past five years, according to Polk. The company reports average age based on an analysis of national vehicle registration data.

The slowdown of the aging of passenger cars is attributed to the low sales volumes and the mix of car and truck sales in the U.S. market in 2008 and 2009, a time in which more trucks than cars were registered, according to Polk. While more trucks were sold over the same timeframe, they showed a faster aging rate.

Polk expects this trend may change in the coming years as CUV and small SUV populations in the U.S. market increased in 2010 and 2011 due to their continued success in the market. The rebound in new-vehicle sales in 2011 and for the next couple of years also will most likely slow down the aging rate seen in the market over the last three years.

"The increasing age of the vehicle fleet, together with the increasing length of ownership, offers significant business growth opportunity for the automotive aftermarket," said Mark Seng, global aftermarket practice leader at Polk. "Dealer service departments and independent repair facilities, as well as aftermarket parts suppliers, will see increased business opportunity with customers in need of vehicle service."

Last year marked the end of the U.S. vehicle population decline that has occurred annually since 2008, according to Polk. The total vehicles in operation (VIO) in July 2011 was slightly more than 240.5 million, an increase of 500,000 units from the year prior, and nearly equal to 2009 VIO. The highest VIO on record was achieved in July 2008, when more than 242 million passenger cars and light trucks were on America's roads.