Agreement between CTS primary care physicians' self-reported practice size vs. the number of Unique Physician Identification Numbers associated with the physician's Tax Identification Number in Medicare claims.

	Practice size based on claims
	1 or 2 n (%)	3-10 n (%)	11-50 n (%)	51 or more n (%)	N = 1,480 (%)
Self-reported practice size, n (%)
1 or 2	720 (93.3)	126 (32.7)	35 (16.3)	9 (5.9)	890 (59.8)
3 or 10	46 (6.3)	221 (65.3)	40 (16.1)	20 (15.3)	327 (22.6)
11 to 50	3 (0.3)	9 (1.7)	135 (62.1)	20 (11.4)	167 (10.4)
51 or more	1 (0.1)	1 (0.3)	11 (5.5)	83 (67.4)	96 (7.2)
Total (% of whole)	770 (52.0)	357 (24.1)	221 (14.9)	132 (8.9)

Based on Medicare claims data for fee-for-service beneficiaries treated at least once by one of 1,480 Community Tracking Study primary care physicians in the year 2005. Excludes CTS physicians who reported working in practice types other than solo and group practices (e.g., hospital-based practice, medical school, group/staff HMO), because these physicians were not asked on the survey to report practice size. The darkest cells on the diagonal indicate agreement (1,159 total, or 78% of 1,480 primary care physicians). Cells shaded in light gray signify physicians for whom practice size based on the number of Unique Physician Identification Numbers associated with their Tax Identification Number was larger than their self-reported practice size (250 total, or 16.9% of 1,480 primary care physicians).