谢谢,楼上版主的提醒,我用所有控制变量的滞后一期的值(相当于前定变量了吧),又回归一次,结果如下:
xtreg lnavegdp odr L.inv_level L.gov L.open L.h_cap,fe
Fixed-effects (within) regression Number of obs = 403
Group variable: id Number of groups = 31
R-sq: within = 0.9088 Obs per group: min = 13
between = 0.2383 avg = 13.0
overall = 0.5835 max = 13
F(5,367) = 731.15
corr(u_i, Xb) = -0.2769 Prob > F = 0.0000
------------------------------------------------------------------------------
lnavegdp | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
odr | -1.719489 .7771724 -2.21 0.028 -3.247759 -.191219
|
inv_level |
L1. | .8871669 .1143736 7.76 0.000 .6622572 1.112077
|
gov |
L1. | 1.430702 .1922166 7.44 0.000 1.052718 1.808686
|
open |
L1. | -.0167211 .1251466 -0.13 0.894 -.2628155 .2293733
|
h_cap |
L1. | 86.22993 3.926188 21.96 0.000 78.50929 93.95058
|
_cons | 8.203082 .103517 79.24 0.000 7.999521 8.406643
-------------+----------------------------------------------------------------
sigma_u | .47248332
sigma_e | .17910588
rho | .87435771 (fraction of variance due to u_i)
------------------------------------------------------------------------------
F test that all u_i=0: F(30, 367) = 25.83 Prob > F = 0.0000
. estimates store FE2
. xtreg lnavegdp odr L.inv_level L.gov L.open L.h_cap,re
Random-effects GLS regression Number of obs = 403
Group variable: id Number of groups = 31
R-sq: within = 0.9028 Obs per group: min = 13
between = 0.5772 avg = 13.0
overall = 0.7555 max = 13
Wald chi2(5) = 3174.81
corr(u_i, X) = 0 (assumed) Prob > chi2 = 0.0000
------------------------------------------------------------------------------
lnavegdp | Coef. Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
odr | -.6281167 .7654699 -0.82 0.412 -2.12841 .8721767
|
inv_level |
L1. | 1.067314 .1158401 9.21 0.000 .8402711 1.294356
|
gov |
L1. | .8546878 .1776853 4.81 0.000 .506431 1.202945
|
open |
L1. | .479122 .0952276 5.03 0.000 .2924793 .6657647
|
h_cap |
L1. | 79.0882 3.687445 21.45 0.000 71.86094 86.31546
|
_cons | 8.031448 .1060791 75.71 0.000 7.823537 8.239359
-------------+----------------------------------------------------------------
sigma_u | .20733637
sigma_e | .17910588
rho | .57266451 (fraction of variance due to u_i)
------------------------------------------------------------------------------
. estimates store RE2
. hausman FE2 RE2, constant sigmamore
删除人力资本滞后一期的回归结果如下:
xtreg lnavegdp odr L.inv_level L.gov L.open,fe
Fixed-effects (within) regression Number of obs = 403
Group variable: id Number of groups = 31
R-sq: within = 0.7889 Obs per group: min = 13
between = 0.1563 avg = 13.0
overall = 0.4439 max = 13
F(4,368) = 343.73
corr(u_i, Xb) = -0.3836 Prob > F = 0.0000
------------------------------------------------------------------------------
lnavegdp | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
odr | 3.029253 1.134087 2.67 0.008 .799148 5.259358
|
inv_level |
L1. | 2.629619 .1251589 21.01 0.000 2.383503 2.875736
|
gov |
L1. | 1.771713 .2910665 6.09 0.000 1.199351 2.344075
|
open |
L1. | 1.475884 .1596491 9.24 0.000 1.161945 1.789823
|
_cons | 7.303729 .1444381 50.57 0.000 7.019701 7.587756
-------------+----------------------------------------------------------------
sigma_u | .53667248
sigma_e | .27210255
rho | .79550246 (fraction of variance due to u_i)
------------------------------------------------------------------------------
F test that all u_i=0: F(30, 368) = 21.90 Prob > F = 0.0000
哪还是存在这个问题?遗漏人力资本这个控制变量,会导致主要解释变量的符号发生变化吗???