- webuse nlswork
- xtset idcode
- xtreg ln_w age ttl_exp tenure 2.race grade, fe //固定效应
- note: 2.race omitted because of collinearity
- note: grade omitted because of collinearity
- Fixed-effects (within) regression Number of obs = 28,099
- Group variable: idcode Number of groups = 4,697
- R-sq: Obs per group:
- within = 0.1443 min = 1
- between = 0.2745 avg = 6.0
- overall = 0.1924 max = 15
- F(3,4696) = 544.06
- corr(u_i, Xb) = 0.1651 Prob > F = 0.0000
- (Std. Err. adjusted for 4,697 clusters in idcode)
- ------------------------------------------------------------------------------
- | Robust
- ln_wage | Coef. Std. Err. t P>|t| [95% Conf. Interval]
- -------------+----------------------------------------------------------------
- age | -0.003 0.001 -2.35 0.019 -0.006 -0.001
- ttl_exp | 0.029 0.002 12.72 0.000 0.025 0.034
- tenure | 0.012 0.001 7.93 0.000 0.009 0.015
- |
- race |
- black | 0.000 (omitted)
- grade | 0.000 (omitted)
- _cons | 1.548 0.027 56.78 0.000 1.494 1.601
- -------------+----------------------------------------------------------------
- sigma_u | .3751722
- sigma_e | .29556813
- rho | .61703248 (fraction of variance due to u_i)
- ------------------------------------------------------------------------------
- gen s = (ln_wage != .) & (age != .) & (ttl_exp != .) & (tenure != .) & (race != .) & (grade != .) //筛选完整观测值
- egen agebar = mean(age) if s, by(idcode)
- egen ttl_expbar = mean(ttl_exp) if s, by(idcode)
- egen tenurebar = mean(tenure) if s, by(idcode)
- egen racebar = mean(race) if s, by(idcode)
- egen gradebar = mean(grade) if s, by(idcode)
- xtreg ln_wage age ttl_exp tenure 2.race grade agebar ttl_expbar tenurebar racebar gradebar, re r //Mundlaks随机效应
- note: gradebar omitted because of collinearity
- Random-effects GLS regression Number of obs = 28,099
- Group variable: idcode Number of groups = 4,697
- R-sq: Obs per group:
- within = 0.1443 min = 1
- between = 0.4338 avg = 6.0
- overall = 0.3251 max = 15
- Wald chi2(9) = 4531.56
- corr(u_i, X) = 0 (assumed) Prob > chi2 = 0.0000
- (Std. Err. adjusted for 4,697 clusters in idcode)
- ------------------------------------------------------------------------------
- | Robust
- ln_wage | Coef. Std. Err. z P>|z| [95% Conf. Interval]
- -------------+----------------------------------------------------------------
- age | -0.003 0.001 -2.35 0.019 -0.006 -0.001
- ttl_exp | 0.029 0.002 12.71 0.000 0.025 0.034
- tenure | 0.012 0.001 7.93 0.000 0.009 0.015
- |
- race |
- black | -0.114 0.025 -4.50 0.000 -0.163 -0.064
- grade | 0.070 0.002 31.29 0.000 0.066 0.075
- agebar | -0.003 0.002 -1.52 0.128 -0.006 0.001
- ttl_expbar | -0.001 0.003 -0.25 0.800 -0.007 0.005
- tenurebar | 0.016 0.003 6.07 0.000 0.011 0.022
- racebar | 0.053 0.024 2.22 0.027 0.006 0.099
- gradebar | 0.000 (omitted)
- _cons | 0.654 0.044 14.84 0.000 0.568 0.740
- -------------+----------------------------------------------------------------
- sigma_u | .27513121
- sigma_e | .29556813
- rho | .46423555 (fraction of variance due to u_i)
- ------------------------------------------------------------------------------
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