Good evening everybody.
I want to run Seemingly Unrelated Regressions (SUR) but the Variance-covariance matrix obtained is singular. But, in my estimations, I found that when I replaced the variance-covariance matrix (singular matrix) by its Jacobian matrix, I am able to run the estimations. I am sceptical about the validity of using this matrix as a kind of feasible generalized least squares.
So my questions are:
- Is it advised or not recommended to use the Jacobian matrix of residual variance-covariance matrix (that is singular) in the context of SUR estimations?
- Are the results, obtained from it, and the subsequent simulations (bootstrap) valid and relevant?
Thank you in advance.
Gratefully