Retirement patterns for self-employed workers.
D003430:Cross-Sectional Studies; D004651:Employment / Q000639:trends*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012106:Research; D012179:Retirement; D012456:Salaries and Fringe Benefits / Q000639:trends; D012943:Social Security; D014481:United States