Conventional unit root tests are known to be unreliable in the presence of permanent volatility shifts. In this paper, we propose a new approach to unit root testing which is valid in the presence of a quite general class of permanent variance changes which includes single and multiple (abrupt...

We show that changes in the innovation covariance matrix of a vector of series can generate spurious rejections of the null hypothesis of co-integration when applying standard residual-based co-integration tests. A bootstrap solution to the inference problem is suggested which is shown to...