It's often taken as a key tenet in any discussion of health policy: The country has too few doctors, and the shortage will only get worse over time. As the population ages and the health law expands insurance, the argument goes, there are simply too few doctors to see the newly-insured and the newly-elderly. There's just one small problem, says Linda Green, a mathematician who has spent two decades studying the health care system: It might not be true. In a new Health Affairs paper, Green argues that forecasting models have greatly overestimated the doctor shortage.