EXHIBIT 1.

Characteristics of Metropolitan Statistical Areas, Physicians, and Physician Groups, by 2014 ACO Penetration, 2008–2010

	Pre-Period (2008–2010)
	2014 ACO Penetration
MSA-level Characteristics	Lowest Quartile (n=73)	Quartile 2 (n=72)	Quartile 3 (n=72)	Highest Quartile (n=72)
Physician-hospital integration, %	13.6	15.7	18.1	23.8**
Physician group size, mean	96.2	77.8	75.5	118.6
Physician HHI, mean	953	987	547	1036
Hospital HHI, mean	4950	4619	3181	4703**
Insurance HHI, mean	2958	2550	2275	2480****
Medicare HMO Penetration, %	8.0	9.4	11.8	5.9
Commercial HMO Penetration, %	16.1	18.6	20.9	21.0****
Inpatient Services Price Index	0.80	0.80	0.78	0.77*
Outpatient Services Price Index	0.96	0.89	0.92	0.96
	Pre-Period (2008–2010)
Physician- or Practice-level (TIN) Characteristics	ACO Non-Participant (in 2012,2013, or 2014)		ACO Participant (in 2012,2013, or 2014)
Practice in a hospital-owned facility, % of physicians	16.9%		20.2%****
Practice acquired, % of physicians	0.1%		0.4%****
Physicians’ mean practice (TIN) size, # of physicians	69.3		130.6****

NOTES

^*p<0.1,

^**p<0.05,

^***p<0.01,

^****p<0.001.

P-values come from a chi-squared test for trend over quartiles of ACO penetration. Physician’s average group size was calculated as the average count of physicians billing for outpatient care within a TIN, weighting each TIN by its share of total physicians in the MSA. MSA is Metropolitan Statistical Area. ACO is Accountable Care Organization. TIN is Tax Identification Number. HHI is Herfindahl Hirschman Index. HMO is Health Maintenance Organization.

Reported P-values come from a chi-squared test for trend over quartiles of ACO penetration. Physician’s average group size was calculated as the average count of physicians billing for outpatient care within a TIN, weighting each TIN by its share of total physicians in the MSA. MSA is Metropolitan Statistical Area. ACO is Accountable Care Organization. TIN is Tax Identification Number. HHI is Herfindahl Hirschman Index. HMO is Health Maintenance Organization.