title: Quantifying income-related inequality in healthcare delivery in the United States.
abstract: BACKGROUND
  Numerous studies have found that high-income Americans use more medical care than their low-income counterparts, irrespective of medical "need." The methods employed in these studies, however, make it difficult to evaluate differences in the degree of income-related inequality in utilization across population subgroups. In this study, we derive a summary index to quantify income-related inequality in need-adjusted medical care expenditures and report values of the index for adults and children in the United States.
  
  
  METHODS
  We used the summary index of income-related inequality in expenditures developed by Wagstaff et al. 1 The source of data for the study was the Household Component of the 1996-1998 Medical Expenditure Panel Survey, which contains person-level data on medical care expenditures, demographic characteristics, household income, and a wide array of health status measures. We used multivariate regression analysis to predict need-adjusted annual medical care expenditures per person by income level and used the predictions to calculate the indices of inequality. Separate indices were calculated for all adults, working-age adults, seniors, and children ages 5 to 17.
  
  
  RESULTS
  For all age groups, predicted expenditures per person, adjusted for medical need, generally increased as income rose. The index of inequality for all adults was +0.087 (95% confidence interval, +0.035, +0.139); for working-age adults, +0.099 (+0.046, +0.152); for seniors, +0.147 (+0.059, +0.235); and for children, +0.067 (+0.006, +0.128).
  
  
  CONCLUSIONS
  There exists income-related inequality in medical care expenditures in the United States, and it favors the wealthy. The inequality is highest among seniors despite Medicare, intermediate among working-age adults, and lowest among children.
authors.affiliation: Division of Research on Children, Youth, and Families, Children's Hospital Los Angeles, Los Angeles, California 90027, USA. alexchen_y@yahoo.com
authors.forename: Alex Y
authors.initials: AY
authors.lastname: Chen
authors.forename: José J
authors.initials: JJ
authors.lastname: Escarce
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D005102:Health Expenditures / Q000706:statistics & numerical data*; D006297:Health Services Accessibility / Q000191:economics*; D006302:Health Services Research; D006305:Health Status Indicators; D006801:Humans; D007182:Income / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D011203:Poverty / Q000706:statistics & numerical data; D012959:Socioeconomic Factors; D014481:United States / Q000453:epidemiology