TABLE 3.

First-stage results

	MA managed care penetration
Lagged payment	0.0221a (0.0051)	0.0244a (0.00438)
IV:	Payment	Payment × year
Observations	60,945,447	60,945,447
R2	0.362	0.25
F-stat	35.4	20.6

Data sources: Medicare beneficiary enrollment files and MA Ratebook Files for 1999–2011. Notes: MA risk penetration is in percentages (ranging from 0 to 100). MA payments are in real 2011 dollars. The payment × year column aggregates the year-specific interaction coefficients to show a comparable average. Standard errors in parentheses (robust, clustered on county).

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.