where Oit represents a binary variable for whether a hospital is efficient or whether a hospital is a high uncompensated care provider, with i indexing a hospital and t indexing time. HMOpenit represents HMO penetration rate. HHIit represents the Herfindahl–Hirschman Index. SNHregnit represents whether a hospital is located in a market where a major safety net hospital is present. Totpopit represents total population. Incomeit represents per capita income. Unempit represents unemployment rate. Mcrshareit represents hospital-specific Medicare share. Mcdshareit represents hospital-specific Medicaid share. Hospitalit represents a vector of hospital characteristics. Yearit is a set of year dummy variables, and Uit is an error term. We primarily used the Stata10.0 software in model analysis.