Strong new-car sales mean more trade-ins, boosting the supply of used vehicles. Discount financing lowers monthly payments for new cars, which means the price of used cars also has to decline to offer the price difference that buyers expect. And the sluggish economy has pushed car rental companies to trim inventories, putting yet more late-model

vehicles on the used-car market, according to the Texas Star-Telegram.

According to ADESA Analytical Services, the average wholesale price for cars in December was 5 percent less than a year earlier. For light trucks, which include pickups and sport utility vehicles, the average was down 2.6 percent.

Paul Taylor, economist for the National

Automobile Dealers Association (NADA), said that there's been a steady rise in the number of vehicles per household. The strong economy of the 1990s led more people to own specialty vehicles, including classic cars, especially in suburban areas where there's room to store the extra vehicle, according to the Star-Telegram.