Table 2.

Characteristics of Respondents and Non-Respondents

		Study cohort (N = 243)	All respondents (N = 386)
		%	%	p-value*
Sex	Male	64	68	0.03
	Female	36	32
Race†	White	84	84	0.96
	Non-white	16	16
Hospital	Academic center	88	88	0.86
	Other	12	12
Specialty	PCP	36	28	<0.001
	Medical	36	41
	Surgical	25	25
	Other	3	7
Practice size†	Solo or 2-physician	14	14	0.57
	3-10 physicians	35	33
	11-50 physicians	32	34
	>50 physicians	19	19
Clinical days per week†	0–1‡	30	27	0.03
	1.5–3	24	34
	3.5 or more	45	39
Years since medical school graduation	Mean (SD)	26.5 (10.9)	25.7 (10.8)	0.051
	Median (IQR)	25 (18–34)	24 (16–34)

P-values calculated using a two-sample t-test or χ² test, as appropriate, and represent comparison of all respondents (see * note below) to study cohort. (IQR = interquartile range, PCP = primary care physician, SD = standard deviation)

*Respondent characteristics taken from survey responses for respondents and from AMA Masterfile or physicians’ organization database for non-respondents

^†Race was missing for 1 respondent, practice size for 4 respondents and clinical days per week for 4 respondents. Missing data were not included in calculations of percentages for each category

‡4 respondents in the study cohort indicated that they work 0 clinical days per week. These clinicians were seeing Medicare patients in 2006; the data set we used to generate our list of relationships, and transitioned into other roles by the time of survey administration in 2010