You hear it so often it's almost a cliché: The nation is facing a serious shortage of doctors, particularly doctors who practice primary care, in the coming years. But is that really the case? Many medical groups, led by the Association of American Medical Colleges, say there's little doubt. "We think the shortage is going to be close to 130,000 in the next 10 to 12 years," says Atul Grover, the group's chief public policy officer. But others, particularly health care economists, are less convinced.