摘要：This paper determines sufficient conditions for a utility function to be associated with an income expansion path whose
dimensionality increases with income i.e. given a finite number of products, the relationship between income and
dimensionality of the consumption vector is given by a step function such that successive intervals on the real number
line (each real number gives an income level) map on to consumption vectors of increasing dimensionality. This
constitutes an important investigation as the rich are observed to exhibit greater consumption variety than the poor and
the same household exhibits increasing product variety as its income increases over time.
