scalar diusion. Among other examples, Stein equation implies that the mean of Hermite polynomials is zero. The GMM approach … contribution of the paper. The second reason for using GMM is that our tests are also valid for time series. In this case, we adopt …

. We establish the direct links between the usual parametric estimation methods, namely, the QMLE, the GMM and the M …-estimation. The ususal univariate QMLE is, under non-normality, less efficient than the optimal GMM estimator. However, the bivariate … QMLE based on the dependent variable and its square is as efficient as the optimal GMM one. A Monte Carlo analysis confirms …