Quadratic Differential Demand Systems and the Retail Demand for Pork in Great Britain

Abstract

The primary objective of this paper is to derive a general synthetic quadratic (rank 3) differential demand system which nests within it a range of testable differential demand models including the quadratic AIDS, CBS, Rotterdam and NBR systems. A model selection test procedure is also outlined. These differential systems are then applied and tested to analyse the monthly retail demand for cuts of pork in Great Britain over the period 1989–2000. The empirical results suggest that a quadratic differential AIDS model is most appropriate for the pork demand system studied, but that the need for inclusion of quadratic income/expenditure terms is not universal for every cut within the demand system. Quadratic expenditure effects were appropriate for pork chops and leg roasts, but log linear expenditure effects were adequate for bellies, shoulders and loin roasts. Roasting cuts were expenditure and own price elastic, with pork loins, chops and bellies all expenditure and own price inelastic.