TABLE 8.

Nonlinear effects of MA managed care penetration

Utilization	Total hospital admissions	Total hospital days	Outpatient ambulatory visits	Outpatient surgical visits	Readmissions	HEDIS composite
Penetration (instrumented)	−0.608    (1.209)	15.54    (10.54)	55.81    (34.73)	6.264a    (1.693)	−0.603    (0.407)	−0.228    (1.422)
Penetration squared (instrumented)	0.00705    (0.0266)	−0.863a    (0.229)	−0.253    (0.731)	−0.103a    (0.0319)	0.00997    (0.00823)	0.0299    (0.0307)
Observations	60,945,447	60,945,447	60,945,447	50,660,647	60,940,793	9,786,818
R2	0.105	0.081	0.152	0.026	0.040	0.033
Penetration “tipping point”	86.24	18.01	220.59	60.82	60.48	7.63

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.

Notes: Table displays only instrumental variable results. MA Penetration and HEDIS composite are percentages (ranging from 0 to 100). Results for utilization are per 1,000 enrollees. Results for outpatient surgical visits are limited to 1999–2010. Standard errors in parentheses (robust, clustered on county). Bottom row shows the value of MA penetration at which the maximum or minimum value of the outcome is achieved that is implied by the coefficients. 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.