Unable to display first-stage estimates; macro e(first) is missing
第一阶段估计无法显示,求问原因。
城市层面的面板数据,工具变量也是城市层面的时变变量。
具体过程如下:
xtset city year,yearly
xi:xtivreg2 lnnum l.lnprice i.year (l.lnprice=l.n2),fe gmm cluster(city_code) first
i.year _Iyear_2007-2013 (naturally coded; _Iyear_2007 omitted)
Warning - duplicate variables detected
Duplicates: __000003
Warning - collinearities detected
Vars dropped: _Iyear_2012 _Iyear_2013
FIXED EFFECTS ESTIMATION
------------------------
Number of groups = 104 Obs per group: min = 3
avg = 4.6
max = 5
Warning - duplicate variables detected
Duplicates: L.lnprice
Warning - collinearities detected
Vars dropped: _Iyear_2012 _Iyear_2013
Unable to display first-stage estimates; macro e(first) is missing
Unable to display summary of first-stage estimates; macro e(first) is missing
2-Step GMM estimation
---------------------
Estimates efficient for arbitrary heteroskedasticity and clustering on city_code
Statistics robust to heteroskedasticity and clustering on city_code
Number of clusters (city_code) = 104 Number of obs = 476
F( 10, 103) = 46.88
Prob > F = 0.0000
Total (centered) SS = 52.35749094 Centered R2 = 0.5088
Total (uncentered) SS = 52.35749094 Uncentered R2 = 0.5088
Residual SS = 25.72005009 Root MSE = .2629
------------------------------------------------------------------------------
| Robust
lnnum | Coef. Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
lnprice |
L1. | -.3538989 .1879312 -1.88 0.060 -.7222373 .0144395
|
_Iyear_2008 | .6060341 .1496306 4.05 0.000 .3127635 .8993046
_Iyear_2009 | .1149394 .1158919 0.99 0.321 -.1122046 .3420833
_Iyear_2010 | .0828028 .0758843 1.09 0.275 -.0659277 .2315332
_Iyear_2011 | .5653012 .056429 10.02 0.000 .4547025 .6759
_Iyear_2012 | 0 (omitted)
_Iyear_2013 | 0 (omitted)
------------------------------------------------------------------------------
Hansen J statistic (overidentification test of all instruments): 0.586
Chi-sq(1) P-val = 0.4438
------------------------------------------------------------------------------
Excluded instruments: L.n2
Duplicates: L.lnprice
Dropped collinear: _Iyear_2012 _Iyear_2013
------------------------------------------------------------------------------