We consider a simple random walk process, a special case ofthe Martingale model, which exhibits a deterministic break in its drift term,for instance, from positive to negative. This particular example can be aplausible model for a time series on exchange rates which displays a persistentcurrency...

It is known that Dickey-Fuller tests can lead to spurious rejections of the unit root nullhypothesis when the true generating process is difference-stationary with a break.Suppose now that an unsuccessful attempt is made to allow for a break, either throughmisplaced dummy variables or through...