Uniform Quasi ML based inference for the panel AR(1) model

This paper proposes new inference methods for panel AR models with arbitrary initial conditions and heteroskedasticity and possibly additional regressors that are robust to the strength of identification. Specifically, we consider several Maximum Likelihood based methods of constructing tests and confidence sets (CSs) and show that (Quasi) LM tests and CSs that use the expected Hessian rather than the observed Hessian of the log-likelihood have correct asymptotic size (in a uniform sense). We derive the power envelope of a Fixed Effects version of such a LM test for hypotheses involving the autoregressive parameter when the average information matrix is estimated by a centered OPG estimator and the model is only second-order identified, and show that it coincides with the maximal attainable power curve in the worst case setting. We also study the empirical size and power properties of these (Quasi) LM tests and CSs.