at Tue 12/13/2005 1:59 PM Victoria Levin wrote:
> My original dependent variable was left-censored at zero, but
> since I had to take logs, I did a monotonic transformation of
> the dependent variable (y+1), and then took logs of that
> [ln(y+1)]. So, my current dependent variable has many zeroes;
> the rest are positive values.
>
> 1) Somehow, when I run the full MLE heckman model:
>
> heckman y x1 x2 x3, select (x1 x2 x3)
<snip>
> I get the following error:
>
> Dependent variable never censored due to selection:
> model would simplify to OLS regression
-heckman- assumes that an observation is censored if y has a missing value. You ensured that there
are no missing values, but by doing so prevented -heckman- from identifying the censored
observations. So just taking the log of y would be enough in your case.
HTH,
Maarten
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting adress:
Buitenveldertselaan 3 (Metropolitan), room Z214
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
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