Some unit root testing situations are more difficult than others. In the case of quarterly industrial production there is not only the seasonal variation that needs to be considered but also the occasionally breaking linear trend. In the current paper we take this as our starting point to...

In search for more efficient unit root tests in the presence of GARCH, some researchers have recently turned their attention to estimation by maximum likelihood. However, although theoretically appealing, the new test is difficult to implement, which has made it quite uncommon in the empirical...