Compare methods

	Tourism Almost Ideal Demand System	Gravity Model of Tourist Flows
Field	Tourism Hospitality	Tourism Hospitality
Family	Regression model	Regression model
Year of origin	1980	2014
Originator	Angus Deaton & John Muellbauer; Gang Li, Haiyan Song & Stephen F. Witt (tourism application)	Clive Morley; Jaume Rossello; Maria Santana-Gallego
Type	System-of-equations consumer demand model	Spatial-interaction / bilateral-flow regression model
Seminal source	Deaton, A., & Muellbauer, J. (1980). An Almost Ideal Demand System. American Economic Review, 70(3), 312-326.	Morley, C., Rossello, J., & Santana-Gallego, M. (2014). Gravity models for tourism demand: theory and use. Annals of Tourism Research, 48, 1-10.
Aliases	Tourism AIDS Model, LAIDS Tourism Demand, Tourism Expenditure Allocation Model, System-of-Equations Tourism Demand	Tourism Gravity Equation, Bilateral Tourist Flow Model, Gravity Model of Tourism Demand, Spatial Interaction Model of Tourism
Related	4	4
Summary	The Almost Ideal Demand System (AIDS), introduced by Angus Deaton and John Muellbauer in 1980, is a system of demand equations grounded in consumer theory that models how a budget is allocated across competing goods through their expenditure shares. Applied to tourism, AIDS treats a tourist's total travel budget as allocated across competing destinations (or expenditure categories), with each destination's budget share depending on relative prices and real total expenditure. Because it estimates all share equations jointly and can impose the restrictions implied by economic theory — adding-up, homogeneity, and symmetry — the model yields a consistent set of income (expenditure) and own- and cross-price elasticities, including how destinations substitute for one another. Gang Li, Haiyan Song, and Stephen Witt's dynamic linear AIDS application demonstrated its value for both explaining and forecasting tourism demand.	The gravity model of tourist flows explains travel between an origin and a destination by analogy to Newton's law of gravitation: bilateral flows increase with the economic 'mass' of both the origin and the destination and decrease with the distance and cost of travel between them. Borrowed from international trade, the model has become a standard tool for analyzing the structural determinants of international tourism, capturing how population, income, distance, common language, shared borders, and historical or cultural ties shape who travels where. Clive Morley, Jaume Rossello, and Maria Santana-Gallego's 2014 Annals of Tourism Research paper grounded the tourism gravity equation in individual utility theory, while the broader trade literature — notably Anderson and van Wincoop's 'multilateral resistance' insight — showed how to specify and estimate it without bias.