Table 1.

Descriptions, Measurements, and Univariate Means for Variables Used in Analysis

Variable	Data Source	Measurement	HSAs with no ACO Mean (SD)	HSAs with 1 or more ACOs Mean (SD)
Health care system characteristics
Mortality	Dartmouth Atlas	Mortality rate per 1,000 Medicare enrollees; age-sex-race adjusted	5.02 (1.36)	4.78 (.57)
Quality score – chronic disease management	Dartmouth Atlas	Factor score of chronic disease management quality measures	−0.09 (.88)	0.21 (.64)
Quality score – diagnostic tests	Dartmouth Atlas	Factor score of diagnostic test quality measures	−0.13 (1.00)	0.34 (.63)
Total Medicare reimbursement per enrollee	Dartmouth Atlas	Dollars, thousands (unadjusted)	8.91 (1.72)	9.33 (1.87)
Acute care hospital bed supply	Dartmouth Atlas	Per 100,000 residents	3.32 (1.42)	2.36 (.73)
Presence of a hospital associated with a system or network	American Hospital Association survey, 2010	Dichotomous (1/0)	0.32 (0.47)	0.46 (0.50)
Physician supply	Dartmouth Atlas	Per 100,000 residents	198.6 (45.99)	209.1 (56.13)
Concentration of primary care providers	100% Medicare claims	Herfindahl-Hirschman Index, thousands	1.90 (3.04)	0.89 (2.05)
Number of primary care medical groups	100% Medicare claims	Number of tax ID numbers for primary care providers per 1,000 residents	0.31 (.21)	0.25 (.16)
Managed care penetration	100% Medicare claims	Proportion of Medicare beneficiaries with Medicare Advantage coverage	0.18 (.14)	0.27 (.15)
Socioeconomic and demographic characteristics
Total population	American Community Survey	Population, thousands	57.3 (105.45)	183.0 (319.52)
Percent in poverty	American Community Survey	Proportion	0.05 (.03)	0.04 (.03)
Percent urban	American Community Survey	Proportion	0.48 (.29)	0.73 (.27)
South	American Community Survey	Dichotomous (1/0)	0.43 (.50)	0.22 (.42)
Midwest	American Community Survey	Dichotomous (1/0)	0.32 (.47)	0.29 (.45)
West	American Community Survey	Dichotomous (1/0)	0.15 (.35)	0.23 (.42)