Invariant (or additive) random utility models (IRUM), that is models whose error term distribution does not depend on any component of the alternatives systematic utility, play an important role in the literature of discrete choice models, thanks to their theoretical and operational simple properties. The objective of this study is to explore the extent of applicability of these simple models, with an ultimate view to providing simpler andmore readily applicable tools to represent complex choice.behaviour. Thisstudy presents a further investigation of the homoskedasticity lemma, which is reformulated by means of a more direct and useful set of constraintsassuring the underlying homoskedastic choice model to be proper. At the current stage of the work, a theoretical proof of this lemma has not been achieved yet, but positive empirical evidence is presented of its validity in contexts with up to ten alternatives. A concluding section indicates how these results could be used in practice to speed up model applications for all kinds of heteroskedastic choice models, including those that are not IRUM. For the covering abstract see ITRD E137145.
Abstract