Tests of the null hypothesis of stationarity against the unit root alternative play an increasingly important role in empirical work in macroeconomics and in international finance. We show that the use of conventional asymptotic critical values for stationarity tests may cause extreme size...

Recent tests using long data series find evidence in favor of long-run PPP (by rejecting either the null hypothesis of unit roots in real exchange rates and relative prices.)

In this paper, we make use of state space models to investigate the presence of stochastic trends in economic time series. A model is specified where such a trend can enter either in the autoregressive representation or in a separate state equation. Tests based on the former are analogous to...

We propose methods to test for common deterministic seasonality, while allowing for possible seasonal unit roots. For this purpose, we consider panel methods, where we allow for individualand for common dynamics. To decide on the presence of seasonal unit roots, we introduce a decision-based...

In this paper we propose a sequential testing procedure to determine the order of differencing in seasonally observed time series processes, which builds existing approaches developed for nonseasonal series. We allow for the possible presence of multiple unit roots at both zero and seasonal...

Recent tests using long data series find evidence in favor of long-run PPP (by rejecting either the null hypothesis of unit roots in real exchange rates and relative prices.)