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. 2005 Oct;40(5 Pt 1):1279–1296. doi: 10.1111/j.1475-6773.2005.00432.x

Table 4.

Difference-in-Differences Model of Total Inpatient Spending for Gainers and Nevers

Fixed-effects (within) Regression
Group Variable (i): baseid
R2: within=0.0036
between=0.0035
overall=0.0007
Corr(u_i,Xb)=-0.8453
Number of obs=13,680
Number of groups=1,401
Obsper group: min=8
avg=9.8
max=16
F(14, 12265)=3.19
Prob> F=0.0000
Total Inpatient Coefficent SE. t p>∣t∣ [95% Confidence Interval]
y1996 187.791 54.95742 3.42 0.001 80.06581 295.5162
y1997 197.1407 79.44047 2.48 0.013 41.42485 352.8565
y1998 278.7367 103.0436 2.71 0.007 76.75515 480.7183
y1999 384.1231 127.8534 3.00 0.003 133.5104 634.7359
y2000 441.7032 150.1892 2.94 0.003 147.3087 736.0976
Age −336.8673 434.3684 −0.78 0.438 −1,188.298 514.5632
Age2 1.850741 2.72236 0.68 0.497 −3.485513 7.186995
Married 10.11199 241.6825 0.04 0.967 −463.6238 483.8478
Income .1033875 1.45629 0.07 0.943 −2.751171 2.957946
Metro −145.9165 716.1161 −0.20 0.839 −1,549.617 1,257.784
HCC Index 121.5006 35.7935 3.39 0.001 51.33974 191.6615
Postperiod 44.89839 37.38742 1.20 0.230 −28.38683 118.1836
Gain −22.63968 135.5702 −0.17 0.867 −288.3786 243.0992
Post × gain −14.70328 63.81229 −0.23 0.818 −139.7854 110.3789
_cons 14,946.69 17,388.75 0.86 0.390 −19,138 49,031.38
sigma_u 931.39804
sigma_e 1,420.2969
rho .30072056 (fraction of variance because of u_i)