Dear Satalist,
I am estimating a conditional logit with the following characteristics:
-Number of decision makers=6,329
-Number of choices=242
-Number of observations=1,531,618 (=6,329*242)
-Decision makers are firms which decide where to locate over a set of 242 location alternatives and independent variables are economic characteristics of the location alternatives.
When estimating the conditional logit I obtain the following message:
"6 groups (1446 obs) dropped due to all positive or all negative outcomes"
clogit choice n2_gdp n2_gdppc n2_mp n2_w2_2 n2_unemp_r l_n2_managg_s n2_fdi n2_popden, group(id)
note: 6 groups (1446 obs) dropped due to all positive or
all negative outcomes.
Iteration 0: log likelihood = -31564.979
Iteration 1: log likelihood = -31562.865
Iteration 2: log likelihood = -31562.865
Conditional (fixed-effects) logistic regression Number of obs = 1529212
LR chi2(8) = 6279.48
Prob > chi2 = 0.0000
Log likelihood = -31562.865 Pseudo R2 = 0.0905
------------------------------------------------------------------------------
choice | Coef. Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
n2_gdp | .2244931 .0260914 8.60 0.000 .1733548 .2756314
n2_gdppc | -.3560138 .033739 -10.55 0.000 -.4221411 -.2898865
n2_mp | .0513986 .0350509 1.47 0.143 -.0172999 .1200972
n2_w2_2 | -.1733384 .047729 -3.63 0.000 -.2668855 -.0797913
n2_unemp_r | -.0770995 .0209851 -3.67 0.000 -.1182295 -.0359696
l_n2_manag~s | .0490496 .0404983 1.21 0.226 -.0303257 .1284248
n2_fdi | .9064167 .0160668 56.42 0.000 .8749263 .937907
n2_popden | .4422606 .0792087 5.58 0.000 .2870145 .5975067
------------------------------------------------------------------------------
As far as I know this means that within those 6 groups (in my case firms) all observations have the same value for the dependent variable.
However I have made several checks and I have one 1 for each group and the rest zeros and also have checked that there are 242 choices for each group.
1/ Can anyone tell me why I am still having this problem?
2/ Is there any way to say stata to tell me which are the 6 groups which are being dropped?
3/ If 6 groups are being dropped, then 6*242=1,452 observations should be dropped but in the message above the observations dropped are 1,446. Why?
I appreciate any comment or help,
Thanks!,
---Rodrigo
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