December featured year-end deals on GM's big pickup trucks; the company offered discounts of up to $9,000 to help clear growing inventory. The move worked. GM cut its full-size pickup supply by more than 20,000 in December to about 222,000.Overall, though, analysts said the industry eased up on promotions such as rebates and low-interest financing. Car and truck buyers paid an average of $31,228 per vehicle last month, up 1.8 percent from December 2011. The year's sales of 14.5 million were far better than the bleak days three years ago when they fell to 10.4 million, a 30-year low as the economy tanked and GM and Chrysler went through bankruptcy protection. But sales still aren't back to the recent peak of around 17 million in 2005. The Polk auto research firm predicted even stronger U.S. sales for 2013, forecasting 15.3 million as the economy continues to improve. Polk, based in Southfield, Mich., expects 43 new models to be introduced, up 50 percent from last year. New models usually boost sales. The firm also predicts a rebound in sales of large pickups and midsize cars. All eight of the top manufacturers are strong and introducing new vehicles, and that should bring competition and lower prices in those segments, according to Tom Libby, lead North American analyst for Polk. But the firm's optimistic forecasts hinge on Washington reaching an agreement on government debt limits and spending cuts.