st: xtivreg vs. xtivreg2

[Sportökonomie <sportoekonomie@gmx.de>]

Dear Statalist,

I am performing a fixed effects instrumental variable panel regression 
by using the following commands:

(1) xtivreg depvar varlist_1 (varlist_2 = varlist_iv), fe
(2) xtivreg2 depvar varlist_1 (varlist_2 = varlist_iv), fe
(3) xtivreg2 depvar varlist_1 (varlist_2 = varlist_iv), fe cluster(id)

For both -xtivreg2- commands I receive the response

"equation not identified; must have at least as many instruments not in 
the regression as there are instrumented variables"

However, I have specified everything analog to the -xtivreg- command. I 
tested myself how to make the xtivreg2 command work, and the only 
solution was to add the 2 instrumented variables also as independent 
variable, which I am sure is not the right way to do.

What does that mean, and how can I adjust the latter two commands to work?

Thanks,
Marc Rohde
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