Maddala, G S; Wu, Shaowen - In: Oxford Bulletin of Economics and Statistics 61 (1999) Special Issue Nov., pp. 631-52
The panel data unit root test suggested by Levin and Lin (LL) has been widely used in several applications, notably in papers on tests of the purchasing power parity hypothesis. This test is based on a very restrictive hypothesis which is rarely ever of interest in practice. The Im-Pesaran-Shin...