Trend and Initial Condition in Stationarity Tests: The Asymptotic Analysis
In this article, we investigate the behaviour of stationarity tests proposed by Müller [Journal of Econometrics (2005) Vol. 128, pp. 195–213] and Harris et al. [Econometric Theory (2007) Vol. 23, pp. 355–363] with uncertainty over the trend and/or initial condition. As different tests are efficient for different magnitudes of local trend and initial condition, following Harvey et al. [Journal of Econometrics (2012) Vol. 169, pp. 188–195], we propose decision rule based on the rejection of null hypothesis for multiple tests. Additionally, we propose a modification of this decision rule, relying on additional information about the magnitudes of the local trend and/or the initial condition that is obtained through pre-testing. The resulting modification has satisfactory size properties under both uncertainty types.
Stationarity test, KPSS test, uncertainty over the trend, uncertainty over the initial condition, size distortion, intersection of rejection decision rule