Dear All,
After running my regression with ivreg2, in last portion of the result I saw error massage which contains the following:
Warning: estimated covariance matrix of moment conditions not of full rank. overidentification statistics not reported, and standard errors and model tests should be interpreted with caution.
Possible causes:
number of clusters insufficient to calculate robust covariance matrix singleton dummy variable (dummy
with one 1 and N-1 0s or vice versa)
partial option may address problem.

Please may you help me in way of solving the problem? Thank You in Advance.