采用固定效应处理面板数据,数据进行对数处理后估计参数由正转负,怎么解释?
LUU代表用地面积,HSR200是一个虚拟变量(取值0和1)
STATA中命令如下:
1)数据不进行对数处理
. xtreg LUU HSR200 i.Year, fe vce(cluster AdminCode)
Fixed-effects (within) regression Number of obs = 1,060
Group variable: AdminCode Number of groups = 265
R-sq: Obs per group:
within = 0.2702 min = 4
between = 0.2236 avg = 4.0
overall = 0.0777 max = 4
F(4,264) = 45.11
corr(u_i, Xb) = 0.1118 Prob > F = 0.0000
(Std. Err. adjusted for 265 clusters in AdminCode)
------------------------------------------------------------------------------
| Robust
LUU | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
HSR200 | 40.8877 13.46118 3.04 0.003 14.38277 67.39263
|
Year |
2008 | 12.17466 1.472148 8.27 0.000 9.276015 15.07331
2010 | 64.98371 6.790302 9.57 0.000 51.61367 78.35375
2013 | 71.76566 7.050435 10.18 0.000 57.88342 85.6479
|
_cons | 138.8109 4.485722 30.95 0.000 129.9785 147.6432
-------------+----------------------------------------------------------------
sigma_u | 212.99957
sigma_e | 74.131083
rho | .8919591 (fraction of variance due to u_i)
------------------------------------------------------------------------------
2)数据进行对数处理
. xtreg lnLUU HSR200 i.Year, fe vce(cluster AdminCode)
Fixed-effects (within) regression Number of obs = 1,060
Group variable: AdminCode Number of groups = 265
R-sq: Obs per group:
within = 0.6403 min = 4
between = 0.2177 avg = 4.0
overall = 0.0236 max = 4
F(4,264) = 193.63
corr(u_i, Xb) = -0.0423 Prob > F = 0.0000
(Std. Err. adjusted for 265 clusters in AdminCode)
------------------------------------------------------------------------------
| Robust
lnLUU | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
HSR200 | -.0664978 .0235318 -2.83 0.005 -.1128318 -.0201639
|
Year |
2008 | .0837592 .0079733 10.50 0.000 .0680598 .0994586
2010 | .383902 .0194631 19.72 0.000 .3455794 .4222247
2013 | .4809142 .0218454 22.01 0.000 .4379007 .5239276
|
_cons | 4.487167 .0096713 463.97 0.000 4.468124 4.50621
-------------+----------------------------------------------------------------
sigma_u | .96475959
sigma_e | .16576273
rho | .97132521 (fraction of variance due to u_i)
------------------------------------------------------------------------------