A two-stage procedure based on impulse saturation is suggested to distinguish mean and variance shifts. The resulting zero-mean innovation test statistic has a non standard distribution, with a nuisance parameter. Hence, simulation-based critical values are provided for some cases of interest....

Monte Carlo evidence is provided as to the efficiency of the impulse saturation estimator in a location-scale model with heavy-tailed distributions. Comparisons show that the IS estimator is always more efficient than the OLS and can even outperform the Method of Moments estimator in some instances.

We establish that under mild conditions, testing for the individual significance of an impulse indicator in the conditional model, selected on the basis of prior testing of its significance in the impulse saturated marginal model does not require bootstrapping critical values. Extensive Monte...