Automakers on Tuesday set a new U.S. sales record for 2015 even as December sales fell short of expectations, and most forecasters said sales should rise to another record this year. 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. Low gasoline prices, easy credit and moderate economic growth boosted the industry. WardsAuto, which provides data used by the U.S.