Dear All, I’m having a problem with DID regression equation. I am using Stata 12.

when I ran the regression

xtreg lnDSL DID ADD EDD SRD BD Inflation LFTA PUCTA TDTA lnTA INVSTA,r

Random-effects GLS regression Number of obs = 4728
Group variable: i Number of groups = 72

R-sq: within = 0.8080 Obs per group: min = 58
between = 0.9538 avg = 65.7
overall = 0.9332 max = 66

Wald chi2(11) = 3116.91
corr(u_i, X) = 0 (assumed) Prob > chi2 = 0.0000

(Std. Err. adjusted for 72 clusters in i)

Robust
lnDSL Coef. Std. Err. z P>z [95% Conf. Interval]

DID .0083772 .0605678 0.14 0.890 -.1103334 .1270878
ADD .168977 .0391338 4.32 0.000 .0922762 .2456778
EDD -.1419524 .0356399 -3.98 0.000 -.2118054 -.0720995
SRD -.0885526 .1545537 -0.57 0.567 -.3914723 .2143671
BD -.4985233 .2932512 -1.70 0.089 -1.073285 .0762385
Inflation .0029831 .0032751 0.91 0.362 -.0034359 .0094021
LFTA -.0068422 .0039584 -1.73 0.084 -.0146005 .0009161
PUCTA -.0089974 .0087924 -1.02 0.306 -.0262302 .0082354
TDTA .0112309 .003142 3.57 0.000 .0050727 .0173892
lnTA 1.130584 .0802098 14.10 0.000 .9733753 1.287792
INVSTA -.0101493 .0039944 -2.54 0.011 -.0179781 -.0023205
_cons -5.251152 .7122417 -7.37 0.000 -6.64712 -3.855184

sigma_u .36208126
sigma_e .31319664
rho .57201446 (fraction of variance due to u_i)

I am wondering why DID model is giving me the result of Random-effects GLS regression .


Thank You