“…The benefits of such an approach are two-fold: one, by using constraints to define the auxiliary model, we sketch a systematic strategy for the choice of an auxiliary model; two, this auxiliary model closely matches the structural model and so for issues of robustness and efficiency this auxiliary model is very useful. However, while highly-useful, the suggestion of Calvet and Czellar (2015) is incomplete, and does not allow for consistent estimation of the structural parameters on its own. That is, since the auxiliary model imposes a number of constraints on the structural model, by definition the auxiliary model can not consistently estimate all the structural parameters, except in the unlikely case where the constraints are satisfied at the true value of the structural parameters.…”