Demand System Estimation

Demand system estimation jointly models how a consumer or population allocates a budget across a complete set of goods, estimating a system of equations — one per good — that relate each good's expenditure share or quantity to all prices and total expenditure. Unlike a single-equation demand curve, a demand system imposes the cross-equation restrictions implied by consumer theory: adding-up (shares sum to the budget), homogeneity (no money illusion), and Slutsky symmetry (consistency of cross-price effects). Classic functional forms include Stone's Linear Expenditure System, the Rotterdam model, and the Almost Ideal Demand System, and the system is estimated with seemingly unrelated regression or full-information methods.