这是我从stata帮助下载的,看看mfx 边际影响系数与回归系数一样(见红字),怎么回事?请高手不吝赐教!
use http://www.stata-press.com/data/r10/abdata, clear
. set matsize 800
. xtabond n l(0/1).w l(0/2).(k ys) yr1980-yr1984 year, lags(2) noconstant
Arellano-Bond dynamic panel-data estimation Number of obs = 611
Group variable: id Number of groups = 140
Time variable: year
Obs per group: min = 4
avg = 4.364286
max = 6
Number of instruments = 40 Wald chi2(15) = 1627.13
Prob > chi2 = 0.0000
One-step results
------------------------------------------------------------------------------
n | Coef. Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
n |
L1. | .7080866 .1455545 4.86 0.000 .4228051 .9933681
L2. | -.0886343 .0448479 -1.98 0.048 -.1765346 -.000734
w |
--. | -.605526 .0661129 -9.16 0.000 -.735105 -.4759471
L1. | .4096717 .1081258 3.79 0.000 .1977491 .6215943
k |
--. | .3556407 .0373536 9.52 0.000 .2824289 .4288525
L1. | -.0599314 .0565918 -1.06 0.290 -.1708493 .0509865
L2. | -.0211709 .0417927 -0.51 0.612 -.1030831 .0607412
ys |
--. | .6264699 .1348009 4.65 0.000 .3622651 .8906748
L1. | -.7231751 .1844696 -3.92 0.000 -1.084729 -.3616214
L2. | .1179079 .1440154 0.82 0.413 -.1643572 .400173
yr1980 | .0113066 .0140625 0.80 0.421 -.0162554 .0388686
yr1981 | -.0212183 .0206559 -1.03 0.304 -.0617031 .0192665
yr1982 | -.034952 .022122 -1.58 0.114 -.0783103 .0084063
yr1983 | -.0287094 .0251536 -1.14 0.254 -.0780096 .0205909
yr1984 | -.014862 .0284594 -0.52 0.602 -.0706414 .0409174
------------------------------------------------------------------------------
Instruments for differenced equation
GMM-type: L(2/.).n
Standard: D.w LD.w D.k LD.k L2D.k D.ys LD.ys L2D.ys D.yr1980 D.yr1981 D.yr1982
D.yr1983 D.yr1984
. mfx, at(mean L.n=-0.06) diag(vce)
Check prediction function does not depend on dependent variables,
covariance matrix, or stored scalars.
dfdx:
.70808656 -.08863433 -.60552603 .40967169 .35564067 -.0599314 -.02117091
.62646995 -.7231751 .11790789 .01130656 -.02121832 -.03495199 -.02870935
-.01486203
dfdx, after resetting dependent variables, covariance matrix, and stored scalars:
.70808656 -.08863433 -.60552603 .40967169 .35564067 -.0599314 -.02117091
.62646995 -.7231751 .11790789 .01130656 -.02121832 -.03495199 -.02870935
-.01486203
Relative difference = 0
Marginal effects after xtabond
y = Linear prediction (predict)
= -.84471245
------------------------------------------------------------------------------
variable | dy/dx Std. Err. z P>|z| [ 95% C.I. ] X
---------+--------------------------------------------------------------------
L.n | .7080866 .14555 4.86 0.000 .422805 .993368 -.06
L2.n | -.0886343 .04485 -1.98 0.048 -.176535 -.000734 1.09584
w | -.605526 .06611 -9.16 0.000 -.735105 -.475947 3.14957
L.w | .4096717 .10813 3.79 0.000 .197749 .621594 3.12676
k | .3556407 .03735 9.52 0.000 .282429 .428852 -.502119
L.k | -.0599314 .05659 -1.06 0.290 -.170849 .050987 -.429181
L2.k | -.0211709 .04179 -0.51 0.612 -.103083 .060741 -.391757
ys | .6264699 .1348 4.65 0.000 .362265 .890675 4.59385
L.ys | -.7231751 .18447 -3.92 0.000 -1.08473 -.361621 4.62901
L2.ys | .1179079 .14402 0.82 0.413 -.164357 .400173 4.66607
yr1980*| .0113066 .01406 0.80 0.421 -.016255 .038869 .225859
yr1981*| -.0212183 .02066 -1.03 0.304 -.061703 .019266 .229133
yr1982*| -.034952 .02212 -1.58 0.114 -.07831 .008406 .229133
yr1983*| -.0287094 .02515 -1.14 0.254 -.07801 .020591 .12766
yr1984*| -.014862 .02846 -0.52 0.602 -.070641 .040917 .057283
------------------------------------------------------------------------------
(*) dy/dx is for discrete change of dummy variable from 0 to 1