Why did hospital costs increase in 1981?
D000328:Adult; D000367:Age Factors; D000368:Aged; D003365:Costs and Cost Analysis / Q000639:trends; D004469:Economics, Hospital / Q000639:trends*; D006764:Hospitals, Community / Q000191:economics; D006801:Humans; D007250:Inflation, Economic / Q000639:trends; D007902:Length of Stay / Q000639:trends; D008875:Middle Aged; D010343:Patient Admission / Q000639:trends; D012456:Salaries and Fringe Benefits / Q000639:trends; D014481:United States