Deriving a Flexible Mixed Demand System: the Normalized Quadratic Model

This article deals with the specification of a locally flexible and theory-consistent system of mixed demand functions, a framework that allows for a rich set of possibilities about what is assumed as exogenous in a demand model. A coherent mixed demand system is derived by using the restricted expenditure function typically studied in the related area of rationed demands. The method is implemented by a new normalized quadratic (NQ) parameterization of the restricted expenditure function. The resulting NQ mixed demand system is illustrated with an application to a nine-good model of the Italian demand for vegetables.