Asymptotic local power of pooled t-ratio tests for unit roots in panels with fixed effects

. This latter test is equivalent to the well-known pooled t test proposed by Levin et al. (2002, Journal of Econometrics 108, 1--24), and its power depends only on the mean of the local-to-unity parameters. This implies that it has the same power against homogeneous and heterogeneous alternatives with the same mean autoregressive parameter. We then compare these tests to a panel version of the Sargan-Bhargava (1983, Econometrica 51, 153--74) statistic for a unit root and the common point-optimal test of Moon et al. (2007, Journal of Econometrics 141, 416--51). Monte Carlo simulations confirm the usefulness of our local-to-unity framework. Copyright Royal Economic Society 2008