TABLE 5.

Effect of MA managed care penetration on outpatient utilization

	Outpatient ambulatory visits		Outpatient surgical visits		Emergency room visits
	OLS	IV	OLS	IV	OLS	IV
Penetration	−0.609       (2.372)	46.87a     (15.96)	−0.159    (0.130)	2.706a    (0.774)	−0.000441    (0.129)	−0.0379    (0.687)
R2	0.152	0.151	0.026	0.026	0.087	0.087
Mean of dep. var.	8,550	8,550	304	304	539	539
10 pct. pt. pen. effect incr. (%)	−0.071	5.482	−0.523	8.901	−0.001	−0.07

Data sources: CMS Medicare claims, Medicare beneficiary enrollment files, and MA Ratebook Files for 1999–2011.

Notes: Results are for years 1999–2011 and contain 60,945,447 observations. Results for outpatient surgical visits are for years 1999–2009 and contain 50,660,647 observations. MA Penetration is in percentages (ranging from 0 to 100). Results for utilization are per 1,000 enrollees. Standard errors in parentheses (robust, clustered on county). Bottom row shows the effect implied by the coefficient of a 10 percentage point increase in penetration on the outcome as a percentage of the mean value of the outcome. Regressions include county and year fixed effects; enrollee-level covariates; and county-level demographics, economic conditions, and health-care workforce.

^ap < 0.01,

^bp < 0.05,

^cp < 0.10.