This paper studies testing for a unit root for large n and T panels in which the cross-sectional units are correlated. To model this cross-sectional correlation, we assume that the data is generated by an unknown number of unobservable common factors. We propose unit root tests in this...

This paper studies testing for a unit root for large n and T panels in which the cross-sectional units are correlated. To model this cross-sectional correlation, we assume that the data is generated by an unknown number of unobservable common factors. We propose unit root tests in this...

We examine properties of the LM test of overdispersion when the alternative is characterized by arbitrary correlated random effects. We first derive a result that a natural test to detect such arbitrary correlated random effects would take the form of the test of conditional moment restriction,...