EXHIBIT 1.

Comparison Of Prospective Attribution And Performance Year Attribution To Simulated Accountable Care Organizations (ACOs)

	Prospective attribution	Performance year attribution
SIMULATED ACOS AND ATTRIBUTION
Number of ACOs with >5,000 patients	1,642	1,642
Mean number of assigned patients	10,668	11,437
Patients assigned through primary care physician	82%	81%
Patients assigned through specialists	18%	19%
ATTRIBUTED POPULATION
Percent visiting ACO during performance year	83	100
Percent visiting an ACO primary care physician during  performance year	69	81
PATIENTS VISITING DURING PERFORMANCE YEAR
Percent attributed	45	57
Percent attributed to primary care physician	36	49
Percent attributed of those visiting a primary care  physician	62	86
PATIENT LOYALTY
Percent of assigned patients’ performance year visits  occurring within the ACO	68	74

SOURCE Authors’ analysis of 100 percent Medicare fee-for-service claims data, 2008–09.