Abrupt changes in the unconditional variance of returns have been recently revealed in many empirical studies. In this paper, we show that traditional KPSS-based tests have a low power against nonstationarities stemming from changes in the unconditional variance. More precisely, we show that...

This paper shows some failures of the KPSS test when the source of the nonstationarity is explained by an unconditional volatility shift. We provide the asymptotic moments of the statistic under general case of shifts in the unconditional variance. We find that these moments remain unchanged...