By the numbers. Physicians.
D000328:Adult; D017677:Age Distribution; D000368:Aged; D004647:Employee Discipline / Q000706:statistics & numerical data; D019538:Health Care Surveys; D006280:Health Workforce; D006801:Humans; D008007:Licensure, Medical / Q000706:statistics & numerical data; D008875:Middle Aged; D010820:Physicians / Q000145:classification / Q000592:standards / Q000600:supply & distribution*; D013038:Specialization; D014481:United States