In this paper, we suggest a new set of regression-based statistics for testing the seasonal unit root null hypothesis. These tests are based on combining conventional Hylleberg et al. (1990) -type seasonal unit root test statistics calculated from both forward and reverse estimation of the...

In this paper we develop new persistence change tests, similar in spirit to those of Kim (2000), Kim et al. (2002) and Busetti and Taylor (2004). While the exisiting tests are based on the maximum over an appropriate sequence of ratios of sub-sample stationarity statistics, our proposed tests...

In this paper we develop new persistence change tests, similar in spirit to those of Kim (2000), Kim et al. (2002) and Busetti and Taylor (2004). While the exisiting tests are based on the maximum over an appropriate sequence of ratios of sub-sample stationarity statistics, our proposed tests...

Being able to correctly characterise an observed time series into its separate difference stationary and trend stationary regimes, should they exist, has important implications for effective model building and forecasting in economics and finance. Existing ratio-based statistics test the null...

Using standardized cumulative sums of squared sub-sample residuals, we propose a new ratio-based test of the null hypothesis that a time series exhibits no change in its persistence structure [specifically that it displays constant I(1) behaviour] against the alternative of a change in...

In the context of regression-based (quarterly) seasonal unit root tests, we examine the impact of initial conditions (one for each quarter) of the process on test power. We investigate the behaviour of the well-known OLS detrended HEGY seasonal unit root tests together with their...

In this paper we consider the issue of testing a time series for a unit root in the possible presence of a break in a linear deterministic trend at some unknown point in the series. We propose a break fraction estimator which, in the presence of a break in trend, is consistent for the true break...

In this paper we focus on two major issues that surround testing for a unit root in practice, namely: (i) uncertainty as to whether or not a linear deterministic trend is present in the data, and (ii) uncertainty as to whether the initial condition of the process is (asymptotically) negligible...