In panel data econometrics the Hausman test is of central importance to select an e±cient estimator of the models' slope parameters. When testing the null hypothesis of no correlation between unobserved heterogeneity and observable explanatory variables by means of the Hausman test model...

Noting that many economic variables display occasional shifts in their second order moments, we investigate the performance of homogenous panel unit root tests in the presence of permanent volatility shifts. It is shown that in this case, panel unit root tests derived under time invariant...

In this dissertation new test statistics for the (panel) unit root hypothesis are presented. Besides a novel approach to testing the unit root hypothesis in univariate time series, the major part of this thesis is dedicated to unit root testing in cross sectionally dependent panels with...