title: Use of econometric models to estimate expenditure shares.
abstract: OBJECTIVE
  To investigate the use of regression models to calculate disease-specific shares of medical expenditures.
  
  
  METHODS
  Medical Expenditure Panel Survey (MEPS), 2000-2003.
  
  
  METHODS
  Theoretical investigation and secondary data analysis.
  
  
  METHODS
  Condition files used to define the presence of 10 medical conditions.
  
  
  RESULTS
  Incremental effects of conditions on expenditures, expressed as a fraction of total expenditures, cannot generally be interpreted as shares. When the presence of one condition increases treatment costs for another condition, summing condition-specific shares leads to double-counting of expenditures.
  
  
  CONCLUSIONS
  Condition-specific shares generated from multiplicative models should not be summed. We provide an algorithm that allows estimates based on these models to be interpreted as shares and summed across conditions.
authors.affiliation: RTI International, 3040 Cornwallis Rd., PO Box 12194, Research Triangle Park, NC 27709-2194, USA.
authors.forename: Justin G
authors.initials: JG
authors.lastname: Trogdon
authors.forename: Eric A
authors.initials: EA
authors.lastname: Finkelstein
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Hoerger
mesh_terms: D000465:Algorithms; D003659:Decision Making, Organizational; D017048:Health Care Costs / Q000706:statistics & numerical data*; D015276:Health Care Rationing; D005102:Health Expenditures / Q000706:statistics & numerical data*; D006801:Humans; D007348:Insurance, Health / Q000191:economics; D008329:Managed Care Programs / Q000191:economics; D017059:Models, Econometric; D014481:United States