Testing for unit roots in three-dimensional heterogeneous panels in the presence of cross-sectional dependence

This paper extends the cross-sectionally augmented IPS (CIPS) test of Pesaran (2006) to a three-dimensional (3D) panel. This 3D-CIPS test is correctly sized in the presence of cross-sectional dependency. Comparing its power performance to that of a bootstrapped IPS (BIPS) test, we Önd that the BIPS test invariably dominates, although for high levels of cross-sectional dependency the 3D-CIPS test can out-perform the BIPS test.