Exhibit 1.

Characteristics Of The Study Population: Effects Of Alternative Quality Contract (AQC) In Blue Cross Blue Shield Of Massachusetts, 2006–10

	AQC groups (intervention)				Non-AQC groups (control) (N=1,339,798)
	2009 cohort (N=428,892)		2010 cohort (N=183,655)
Characteristic	Pre AQC (2006–08)	Post AQC (2009–10)	Pre AQC (2006–09)	Post AQC (2010)	Pre AQC (2006–08)	Post AQC (2009–10)
Age (years)	34.4 ± 18.6	35.5 ± 18.5	36.2 ± 18.2	37.9 ± 18.2	35.2 ± 18.7	35.3 ± 19.0
Percent female	52.6	52.1	51.7	52.0	51.8	51.1
Health risk scorea
Mean	1.08	1.16	1.18	1.25	1.11	1.15
Interquartile range	0.12–1.29	0.13–1.39	0.13–1.43	0.14–1.53	0.10–1.31	0.11–1.37
Cost sharing (%)
Mean	13.9	16.1	14.4	16.7	13.8	15.8
Interquartile range	11.3–16.3	11.0–18.6	11.2–17.3	12.7–18.5	11.2–16.3	11.0–18.6

Source/Notes: SOURCE Authors’ analysis of 2006–2010 Blue Cross Blue Shield of Massachusetts enrollment data. NOTES Plus–minus values are means ± SD (standard deviation). The total number of enrollees in the intervention and control groups exceeds 1,655,745 because there were enrollees who had one primary care physician in the intervention group and another in the control group for at least one year in each case. Cost sharing represents the average percentage of spending paid for out of pocket by the enrollee on common services, defined by using the most frequent Current Procedural Terminology (CPT) codes.

^aThe health risk score takes into account the health status of the enrollee and expected spending. See Note 21 in text.