A generalised extreme value model admitting substitution and complementarity between alternatives

A model of comparatively simple structure, yet free of the IIA restrictions, is developed, but unlike many non-IIA models no intrinsically nonlinear parameters are introduced and estimation is similar to the logit. Complementary as well as substitute alternatives are allowable as well as complementary pairwise relationships between two alternatives without affecting substitutional relationships between other alternatives. Cross-elasticities, which in the logit depend only on characteristics and parameters of the alternative changed, now depend also on the alternative affected and on other previously “irrelevant” alternatives.