The standard Dickey–Fuller (DF) test is routinely employed to analyse the integrated nature of economic and financial time series. However, recent research has shown the test to suffer severe size distortion in the presence of breaks in innovation variance under the unit root null hypothesis....

Using Monte Carlo simulation, threshold autoregressive (TAR) and momentum-threshold autoregressive (MTAR) asymmetric unit root tests are examined in the presence of generalised autoregressive conditional heteroskedasticity (GARCH). It is shown that TAR and MTAR unit root tests exhibit greater...

Using local-to-unity detrending, a modified momentum-threshold autoregressive test is derived to allow the unit root hypothesis to be tested against an alternative of asymmetric stationarity about a deterministic trend. Monte Carlo evidence is presented to show the increased power of the...

The research of Kim and Schmidt (J. Economet., 1993, 59, 287-300) is extended to examine the properties of modified Dickey-Fuller unit root tests in the presence of generalized autoregressive conditional heteroskedasticity (GARCH). Using Monte Carlo simulation, the properties of the tests are...