“…In particular, the simulations show that the new CUII estimator offers a substantial improvement over standard 2SLS and robust GMM as it does not rely on the construction of optimal instruments and, even more importantly, on the joint relevance of such instruments. In independent recent work that appeared after our paper was completed, Bao, Liu, and Yang (2020) extended results in KPR to SARX models with heteroskedastic error terms, and suggested an II-type transformation that produces results comparable to our findings reported in Sections 3 and 4. Bao et al (2020) adopted a different parameterization of the (nonconstant) variancecovariance matrix of the disturbances, resulting in a different asymptotic variance for their estimator.…”