st: No Standard Errors in MLOGIT

[Charles Parekh <charles.parekh@nyu.edu>]

Hello,

I have a question about the mlogit command in stata.

I am using Stata 9/SE on a Windows XP machine. I am using the syntax

mlogit yvar x1 x2 x3 x4, robust

When I do so, I get output that makes sense except for the constant 
produces a coefficient but no standard error. Is there some reason for 
this? I am assuming there is some within group collinearity, but why 
would the procedure produce a coefficient and no standard error? Also, 
if there is multicollinearity, it is not perfect multicollinearity, I 
have checked that.

Any idea?

Thanks,

Charlie

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