This paper contains a Lagrange multiplier test of the hypothesis that the covariance matrix of a multivariate time series model is constant over time. It is further assumed that under the alternative, the error variances are time-varying whereas the correlation remain constant over time. Under...

This paper considers testing the unit root hypothesis against a smooth transition autoregressive model as the alternative. The model specification makes it possible to discriminate between nonstationary random walk and stationary nonlinear processes. Some new limit results are presented,...

This paper considers the modelling and forecasting of the Icelandic business cycle. The method of selecting monthly variables, coincident and leading, that mimic the cyclical behavior of the quarterly GDP is described. The general business cycle is then modelled by a vector autoregressive, VAR,...