DETROIT (AP) — A steadily improving economy and strong December sales lifted the American auto industry to its best performance in five years in 2012, especially for Volkswagen and Japanese-brand vehicles, and experts say the next year should be even better. Carmakers on Thursday announced their final figures, which totaled 14.5 million — 13 percent better than 2011. More than three years after the federal government's $62 billion auto-industry bailout, Americans had plenty of incentive to buy new cars and trucks in the year just ended.