This study considers the possibility of estimating a Dickey-Fuller regression, constraining the autoregressive parameter to be at most one, and imposing prior knowledge of the sign of the drift parameter. In spite of apparently encouraging asymptotic results, it emerges that no feasible test of...

In this paper we introduce a new test of the null hypothesis of no cointegration between a pair of time series. For a very simple generating model, our test compares favourably with the Engle-Granger/Dickey-Fuller test and the Johansen trace test. Indeed, shortcomings of the former motivated the...

We analyse the case where a unit-root test is based on a Dickey-Fuller regression the only deterministic term of which 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...