AComparative study of unit root tests with panel data and a new simple test（18）

G. S.Maddala and Shaowen Wu

(H. D.Thoreau: Walden)

CONCLUSIONS

1.      Themain conclusion of the paper

2，Onemajor problem with the literature on unit root and cointegration tests in paneldata

3，  Itis very important to bear in mind Thoreau's admonition quoted at the beginningof our paper.