A framework for duality theory is set forth, based on the model-independent role of homotheties. An expansion vector field is introduced as global generator of pure expansion effects, in terms of which to deepen the differential aspects of preference symmetries, fundamental identities and...

A 2-parameter class of ordinal utility functions over a pair of goods is discussed with respect to general traits of preferences for luxury. The class contains Cobb-Douglas functions as no-luxury limit; its analytical tractability is probed by simple closed form solutions for Marshallian demand...