With Vermont leading the way, five of New England's six states rank in the top six for primary care doctors per capita, according to data from the Association of American Medical Colleges. The sixth, Connecticut, ranks 12th. As the national shortage of primary care doctors expected to increase after the federal Affordable Care Act takes full effect next year, some are looking to New England's states with an eye to what they've been doing right. Several factors contribute to New England's relatively strong position. Among them: strong public health programs ensuring that high percentages of residents have health coverage, meaning fewer doctors deliver uncompensated care.