This repeated subsampleis used as the data samples in this paper. We restrict the individual-level data sample to adults who are age 18 years and over. In addition, the 2001 Area Resource File (ARF) is linked to the CTS Household Survey by state and county to provide physicians’ characteristics at the market level, as well as communities’ characteristics. The summary statistics about the data sample, which is weighted to control for stratification, clustering and oversampling to represent the US national population, are presented in Table 1.