Although the t-ratio variant of the Dickey-Fuller test is the most commonly applied unit root test in practical applications, it has been known for some time that readily implementable, more powerful modifications are available. We explore the large sample properties of five of these modified...

We analyse the case where a unit root test is based on a Dickey-Fuller regression whose only deterministic term is a fixed intercept. Suppose, however, as could well be the case, that the actual data generating process includes a broken linear trend. It is shown theoretically, and verified...

We present a test of the null hypothesis of stationarity against unit root alternatives for panel data that allows for arbitrary cross- sectional dependence. We treat the short run time series dynamics non- parametrically and thus avoid the need to fit separate models for the individual series....

We consider the power of unit root tests for different deviations of the initial observation from the deterministic component of the series. Following recent work highlighting the relative power performance of extant tests, we propose a new procedure based on a data-dependent weighted average of...