DETROIT — Strong US sales in December capped a remarkable year for the auto industry — especially Japanese brands — and 2013 should be even better. Sales of new cars and trucks are expected to total 14.5 million. That is 13 percent better than in 2011 and the best performance in five years.

In 2012, Americans had plenty of incentives to buy. Unemployment eased. Home sales and prices rose. And the average age of a car topped 11 years. Banks offered low interest rates and greater access to loans, even for those with weak credit.