Table 5.
Difference-in-Differences Model of Physician Spending for Gainers and Nevers
| Fixed-Effects (within) Regression Group Variable (i): baseid R2: within=0.0066 between=0.0242 overall=0.0098 Corr(u_i, Xb)=-0.3113 |
Number of obs=45,384 Number of groups=4,054 Obsper group: min=8 avg=11.0 max=16 F(14,41316)=19.68 Prob>F=0.0000 |
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|---|---|---|---|---|---|---|
| Total Physician | Coefficent | SE | t | p>∣t∣ | [95% Confidence Interval] | |
| y1996 | 9.100585 | 3.430918 | 2.65 | 0.008 | 2.375913 | 15.82526 |
| y1997 | 14.25092 | 4.949754 | 2.88 | 0.004 | 4.549295 | 23.95254 |
| y1998 | 22.28622 | 6.533179 | 3.41 | 0.001 | 9.481051 | 35.09139 |
| y1999 | 29.73888 | 8.153666 | 3.65 | 0.000 | 13.75752 | 45.72024 |
| y2000 | 33.8768 | 9.628832 | 3.52 | 0.000 | 15.00408 | 52.74951 |
| Age | −20.6048 | 20.90089 | −0.99 | 0.324 | −61.57099 | 20.36139 |
| Age2 | .122362 | .1327581 | 0.92 | 0.357 | −.1378466 | .3825706 |
| Married | −17.61857 | 12.10421 | −1.46 | 0.146 | −41.34308 | 6.105949 |
| Income | −.0014219 | .0547972 | −0.03 | 0.979 | −.1088255 | .1059817 |
| Metro | −22.75821 | 37.74338 | −0.60 | 0.547 | −96.73604 | 51.21962 |
| HCC Index | 29.52116 | 3.312933 | 8.91 | 0.000 | 23.02774 | 36.01458 |
| Postperiod | 19.03616 | 2.345403 | 8.12 | 0.000 | 14.43912 | 23.6332 |
| Gain | .8919971 | 7.274963 | 0.12 | 0.902 | −13.36709 | 15.15108 |
| Post × Gain | −2.738953 | 4.122824 | −0.66 | 0.506 | −10.81978 | 5.341871 |
| _cons | 900.9817 | 827.3328 | 1.09 | 0.276 | −720.6082 | 2,522.572 |
| sigma_u | 94.073779 | |||||
| sigma_e | 168.21478 | |||||
| rho | .23824516 (fraction of variance because of u_i) | |||||