Automakers on Tuesday set a new U.S. sales record for 2015 even as December sales fell short of expectations, and most forecasters said the new year will be even better. For full year 2015, U.S. sales hit a record of 17.47 million vehicles, breaking the mark of 17.41 million vehicles in 2000, according to Autodata Corp, as low gasoline prices, easy credit and moderate economic growth boosted the industry. Autodata said December sales on an annualized rate, accounting for seasonal factors, were 17.34 million vehicles, well below the 18.1 million vehicles expected by a Thomson Reuters poll of 38 economists and analysts. “The U.S. economy continues to expand and the most important factors that drive demand for new vehicles are in place, so we expect to see a second consecutive year of record industry sales in 2016,” said Mustafa Mohatarem, chief economist for General Motors Co ( GM.N ). […]