"Under the Patient Protection and Affordable Care Act (PPACA), Medicaid enrollment is expected to grow by 16 million people by 2019, an increase of more than 25 percent. Given the unwillingness of many primary care physicians (PCPs) to treat new Medicaid patients, policy makers and others are concerned about adequate primary care capacity to meet the increased demand. States with the smallest number of PCPs per capita overall—generally in the South and Mountain West—potentially will see the largest percentage increases in Medicaid enrollment, according to a new national study by the Center for Studying Health System Change (HSC). In contrast, states with the largest number of PCPs per capita—primarily in the Northeast—will see more modest increases in Medicaid enrollment. Moreover, geographic differences in PCP acceptance of new Medicaid patients reflect differences in overall PCP supply, not geographic differences in PCPs’ willingness to treat Medicaid patients."