Hello,
Could any one help me understand why the coefficients of the natural log of
a dependent variable are close, but not equivalent to the marginal effect of
the same dependent variable estimated with the eydx option (dlogy/dx).
Assuming the same sample, regressors, etc...
A numerical example use the auto dataset follows below.
Many thanks,
JP
use auto
gen lnprice=ln(price)
regress lnprice mpg rep78 headroom trunk
----------------------------------------------------------------------------
--
lnprice | Coef. Std. Err. t P>|t| [95% Conf.
Interval]
-------------+--------------------------------------------------------------
--
mpg | -.0356709 .008907 -4.00 0.000 -.0534646
-.0178772
rep78 | .1079145 .0436081 2.47 0.016 .0207973
.1950316
headroom | -.1041363 .0614146 -1.70 0.095 -.2268261
.0185535
trunk | .0227757 .0136441 1.67 0.100 -.0044815
.0500329
_cons | 9.026498 .3126985 28.87 0.000 8.401811
9.651185
----------------------------------------------------------------------------
--
regress price mpg rep78 headroom trunk
----------------------------------------------------------------------------
--
price | Coef. Std. Err. t P>|t| [95% Conf.
Interval]
-------------+--------------------------------------------------------------
--
mpg | -252.6424 70.48498 -3.58 0.001 -393.4523
-111.8325
rep78 | 626.8463 345.0914 1.82 0.074 -62.55297
1316.246
headroom | -613.8173 486.003 -1.26 0.211 -1584.72
357.0853
trunk | 121.0197 107.9722 1.12 0.267 -94.67944
336.7189
_cons | 9545.797 2474.533 3.86 0.000 4602.35
14489.24
----------------------------------------------------------------------------
--
mfx, eydx
Elasticities after regress
y = Fitted values (predict)
= 6146.0435
----------------------------------------------------------------------------
--
variable | ey/dx Std. Err. z P>|z| [ 95% C.I. ] X
---------+------------------------------------------------------------------
--
mpg | -.0411065 .01165 -3.53 0.000 -.063945 -.018268
21.2899
rep78 | .1019918 .05638 1.81 0.070 -.008514 .212497
3.4058
headroom | -.0998719 .07923 -1.26 0.208 -.255169 .055425
3
trunk | .0196907 .0176 1.12 0.263 -.014796 .054177
13.9275
----------------------------------------------------------------------------
--
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
