TABLE 6.

Effect of MA managed care penetration on utilization for enrollees with chronic conditions

	Total hospital admissions	Hospital medical days	Hospital surgical days	Outpatient ambulatory visits	Outpatient surgical visits
Penetration (instrumented)	−0.446    (0.799)	−22.39a     (8.480)	−6.568b    (3.290)	76.48a       (22.85)	3.158a    (0.958)
R2	0.098	0.081	0.024	0.103	0.027
Mean of dep. var.	545	2,240	960	10,865	377
10 pct. pt. pen. incr. effect (%)	−0.818	−9.996	−6.842	7.039	8.377

Data sources: CMS Medicare claims data inpatient, outpatient, and carrier files, Medicare beneficiary enrollment files, and MA Ratebook Files for 1999–2011. Data are limited to beneficiaries with at least one chronic condition (including diabetes, heart disease, or chronic obstructive pulmonary disease).

Notes: Results are for years 1999–2011 and contain 25,974,810 observations. Results for outpatient surgical visits are for years 1999–2009 and contain 23,225,305 observations. MA Penetration is in percentages (ranging from 0 to 100). Results for utilization are per 1,000 enrollees. Regressions include county and year fixed effects; enrollee-level covariates; and county-level demographics, economic conditions, and health-care workforce. 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.

^ap < 0.01,

^bp < 0.05,

^cp < 0.10.