Polk predicted a handful of other trends for 2013. Sales will grow for big pickup trucks, which are very profitable for automakers. Demand has been depressed for five years due to the weak economy, but should get a lift in 2013 thanks to redesigned trucks from GM, Toyota and Ford.
Polk also said the midsize sedan segment will continue to lead the industry. It's now at 18.5 percent of the market, 2 percentage points larger than any other type of segment.
"Recent redesigns of nearly every vehicle in the midsize segment are forcing more competition and continued growth," said Tom Libby, Polk's lead North American analysts.
Polk joins many other analysts in predicting 2013 sales at or above 15 million. The consulting firm LMC Automotive, for instance, expects 2013 sales of around 15 million, up from 14.5 million in 2012.
Auto sales peaked at about 17 million in 2005, but dropped to 10.4 million in 2009, the lowest level in more than three decades.