. 2011 Nov 18;47(3 Pt 1):1008–1029. doi: 10.1111/j.1475-6773.2011.01351.x

Table 3.

Regression Results

	% Received Intensive Treatment		% Treated Within 1 Day		Average No. of Procedures		% Die in Hospital		Average Length of Stay

	(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
Panel 1: OLS without hospital referral region trends
Merged share	0.048 (0.010)^***	0.043 (0.009)^***	0.084 (0.018)^***	0.077 (0.018)^***	0.522 (0.122) ^***	0.452 (0.122) ^***	0.005 (0.001) ^***	0.002 (0.001)^*	0.230 (0.145)	0.054 (0.102)
R²	0.6	0.68	0.48	0.52	0.48	0.52	0.11	0.16	0.69	0.69
Panel 2: OLS with hospital referral region trends
Merged share	0.048 (0.008)^***	0.050 (0.008)^***	0.013 (0.021)	0.016 (0.022)	0.285 (0.120)^**	0.276 (0.121)^**	0.003 (0.002)^*	0.002 (0.001)	0.277 (0.126)^**	0.221 (0.119)^*
R²	0.62	0.69	0.52	0.55	0.53	0.56	0.11	0.16	0.69	0.7
Panel 3: IV without hospital referral region trends
Merged share	0.043 (0.009)^***	0.041 (0.008)^***	0.109 (0.019)^***	0.106 (0.018)^***	0.593 (0.122)^***	0.533 (0.119)^***	0.007 (0.002)^***	0.003 (0.001)^**	0.330 (0.155)^**	0.195 (0.144)
R²	0.6	0.68	0.48	0.52	0.48	0.52	0.11	0.16	0.69	0.69
Panel 4: IV with hospital referral region trends
Merged share	0.045 (0.010)^***	0.050 (0.008)^***	0.029 (0.022)	0.035 (0.022)	0.395 (0.125)^***	0.392 (0.124)^***	0.005 (0.002)^***	0.003 (0.002)^*	0.414 (0.124)^***	0.300 (0.116)^***
R²	0.62	0.69	0.52	0.55	0.53	0.56	0.11	0.16	0.69	0.7
Control variables		X		X		X		X		X
Observations	47,396	47,396	47,396	47,396	47,396	47,396	47,396	47,396	47,396	47,396

Notes. Robust standard errors in parentheses.

Significant at 10%;

^**

Significant at 5%;

^***

Significant at 1%.

Zip codes are only included if they have 15 or more discharges in every quarter. All regressions include quarter and zip code fixed effects and are weighted by the number of heart disease discharges. Standard errors are clustered by zip code. Control variables include the percentage of discharges with demographic characteristics such as race, gender, and age categories; with expected payer such as Medicare and private insurance; with comorbidities such as hypertension, diabetes, and heart failure; admission through the ER; and a constant.