TABLE 4.

Effect of MA managed care penetration on inpatient utilization

	Total hospital admissions		Total hospital days
	OLS	IV	OLS	IV
Penetration	0.128    (0.0949)	−0.359    (0.478)	−1.228c       (0.713)	−14.95a       (5.434)
R2	0.105	0.105	0.081	0.081
Mean of dep. var.	360	360	2,035	2,035
10 pct. pt. pen. incr. effect (%)	0.356	−0.997	−0.603	−7.346

	Hospital medical days		Hospital surgical days
	OLS	IV	OLS	IV
Penetration	−0.377       (0.571)	−12.47a       (4.673)	−0.932a    (0.308)	−3.636b    (1.850)
R2	0.082	0.082	0.022	0.022
Mean of dep. var.	1,365	1,365	665	665
10 pct. pt. pen. incr. effect (%)	−0.276	−9.136	−1.402	−5.468

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

Notes: Number of observations: 60,945,447. MA Penetration is in percentages (ranging from 0 to 100). Results for utilization are per 1,000 enrollees. 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.