Against tough competition from other sandwiches and flat to declining restaurant traffic, burgers ordered at U.S. restaurants and foodservice outlets had a banner year in 2014, finds foodservice market research from The NPD Group, a leading global information company. There were 9 billion servings of burgers ordered at U.S. restaurants and foodservice outlets last year, an increase of 3 percent compared to prior year, according to NPD’s ongoing foodservice market research.