The increasing dispersion of specialists.
D000293:Adolescent; D000328:Adult; D002568:Certification; D002648:Child; D002755:Choice Behavior; D005260:Female; D006285:Health Planning; D006296:Health Services; D006301:Health Services Needs and Demand; D006280:Health Workforce; D006801:Humans; D010820:Physicians / Q000600:supply & distribution*; D013038:Specialization; D013044:Specialty Boards; D014481:United States; D014505:Urban Population