Nonstationary fractionally integrated time series may possibly be fractionally cointegrated. In this paper we propose a test for the null hypothesis of no cointegration. It builds on a static cointegration regression of the levels of the variables as a first step. In a second step, a univariate LM test is applied to the single equation regression residuals. However, it turns out that the applic...

This paper considers alternative methods of testing cointegration in fractionally integrated processes, using the bootstrap. The special feature of the fractional case is the dependence of the asymptotic null distributions of conventional statistics on the fractional integration parameter. Such tests are said to be asymptotically non-pivotal, and conventional asymptotic tests are therefore not ...

For univariate time series we suggest a new variant of efficient score tests against fractional alternatives. This test has three important merits. First, by means of simulations we observe that it is superior in terms of size and power in some situations of practical interest. Second, it is easily understood and implemented as a slight modification of the Dickey-Fuller test, although our score...

In this paper we introduce a class of nonlinear data generating processes (DGPs) that are "rst order Markov and can be represented as the sum of a linear plus a bounded nonlinear component. We use the concepts of geometric ergodicity and of linear stochastic comovement, which correspond to the linear concepts of integratedness and cointegratedness, to characterize the DGPs. We show that the sta...