Slide Presentation from the AHRQ 2007 Annual Conference

Control Variables

• X_it: a vector of other explanatory variables for hospital i in year t
  • % Medicare patient days
  • % Medicaid days
  • The hospital mean of the Charlson comorbidity score
  • % surgical discharges
  • Market concentration (HHI)
  • County-level per capita income
  • County-level population density
• Zt is a vector of the year dummy variables which will adjust the effects of unmeasured, time-specific factors