We consider questions of efficiency and redundancy in the GMM estimation problem in which we have two sets of moment conditions, where two sets of parameters enter into one set of moment conditions, while only one set of parameters enters into the other. We then apply these results to a...

We derive a corrected distance metric (DM) test of general restrictions. The correction factor depends on the value of the uncorrected statistic and the new statistic is Bartlett-type. In the setting of covariance structure models, we show using simulations that the quality of the new...

Optimal GMM is known to dominate Gaussian QMLE in terms of asymptotic efficiency (Chamberlain, 1984). I derive a new condition under which QMLE is as efficient as GMM for a general class of covariance structure models. The condition trivially holds for normal data but also identifies non-normal...

We consider stochastic frontier models in a panel data setting where there is dependence over time. Current methods of modelling time dependence in this setting are either unduly restrictive or computationally infeasible. Some impose restrictive assumptions on the nature of dependence such as...

Several recent papers (e.g., Newey et al., 2005; Newey and Smith, 2004; Anatolyev, 2005) derive general expressions for the second-order bias of the GMM estimator and its first-order equivalents such as the EL estimator. Except for some simulation evidence, it is unknown how these compare to the...