Table 4. Differences in Patient Panel and Patient Characteristics Between ACO-Participating Physician Groups and Nonparticipating Physician Groups by Initial Year of Participation^a.

Characteristics	Physician-Group Level		Patient Level
	Percentage Point Difference in Patient Characteristic With ACO Participation (95% CI)	P Value	Percentage Point Difference in Patient Characteristic With ACO Participation (95% CI)	P Value
2012 Cohort
Black	−0.2 (−4.9 to 4.5)	.94	−1.2 (−6.6 to 4.1)	.65
Dually enrolled	4.0 (−1.0 to 8.9)	.12	3.6 (−2.3 to 9.5)	.23
Living in high-poverty zip code	15.1 (−7.1 to 37.3)	.18	11.3 (−14.9 to 37.4)	.40
High risk	2.0 (0.3 to 3.7)	.02	3.5 (0.8 to 6.2)	.01
No.	63 714	NA	4 801 631	NA
2013 Cohort
Black	0.8 (−2.7 to 4.3)	.65	1.4 (−5.2 to 8.0)	.67
Dually enrolled	1.6 (−0.5 to 3.6)	.13	1.1 (−2.9 to 5.1)	.58
Living in poverty	−7.4 (−19.3 to 4.5)	.22	−18.3 (−45.5 to 8.9)	.19
High risk	1.5 (0.4 to 2.5)	.006	−0.1 (−2.5 to 2.4)	.94
No.	62 931	NA	4 746 511	NA
2014 Cohort
Black	0.2 (−1.4 to 1.7)	.85	−0.5 (−4.0 to 3.1)	.80
Dually enrolled	0.5 (−0.8 to 1.7)	.48	0.9 (−2.3 to 4.0)	.59
Living in poverty	−0.3 (−8.2 to 7.6)	.94	−4.5 (−30.1 to 21.1)	.73
High risk	1.0 (0.1 to 1.9)	.03	1.7 (−0.6 to 4.0)	.15
No.	62 598	NA	4 694 541	NA

Abbreviations: ACO, accountable care organization; NA, not applicable.

^aAll regressions adjust for the number of physicians in the physician group, the percentage of physicians who were specialists, the percentage of physicians affiliated with a health system, and the percentage of physicians who were hospital based and included hospital service area fixed effects.