Persons with and without a regular source of medical care.
D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006291:Health Policy / Q000639:trends*; D006297:Health Services Accessibility / Q000639:trends*; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D012017:Referral and Consultation / Q000639:trends*; D014481:United States