Let me reformulate the whole problem. I have to estimate
Y1=X1*b1+X2*b2+X3*b3
Y2=X1*t1+X2*t2+X3*t3
where X1 X2 and X3 are the same in both equations. I have to estimate these
two imposing the restriction t1/b1=t2/b2. I have the additional issue that
X3 (I have several variables in X3, so I was just using a more compact form)
is potentially correlated with the errors. How can I tackle the whole thing
imposing the restrictions and without having to specify other equations for
the endogenous variables in X3?
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