Dear Statalist,
I got a error message and cannot figure out the reason. Could you
help?
I am runing the following model:
Y=aT+bZ+cTZ+dX,
Here, TZ=T*Z is the interaction term, T is the time dummy (=1 after
the policy change), and Z are the continuous endogenous treatments, X
are exogenous variables.
The command I use is: ivreg2 Y T X (TZ Z=W V TW TV)
I got an error message for the first stage regression:
Error: covariance matrix of moment conditions not of full rank;
specification
test stats not reported and standard errors above may be
meaningless.
This should be caused by collinearity, because collinearity variables
have been automatically dropped by stata.
Thank you very much.
Binzhen
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