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	Tourism Almost Ideal Demand System	Tourism Demand Elasticity Modeling
Field	Tourism Hospitality	Tourism Hospitality
Family	Regression model	Regression model
Year of origin	1980	1994
Originator	Angus Deaton & John Muellbauer; Gang Li, Haiyan Song & Stephen F. Witt (tourism application)	Geoffrey I. Crouch
Type	System-of-equations consumer demand model	Econometric demand-elasticity estimation
Seminal source	Deaton, A., & Muellbauer, J. (1980). An Almost Ideal Demand System. American Economic Review, 70(3), 312-326.	Crouch, G. I. (1994). The Study of International Tourism Demand: A Review of Findings. Journal of Travel Research, 33(1), 12-23.
Aliases	Tourism AIDS Model, LAIDS Tourism Demand, Tourism Expenditure Allocation Model, System-of-Equations Tourism Demand	Tourism Income Elasticity, Tourism Price Elasticity, Elasticity of International Tourism Demand, Tourism Demand Sensitivity Analysis
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.	Tourism demand elasticity modeling estimates how responsive tourist demand is to changes in its key drivers, above all source-market income and the price of travel. The income elasticity measures the percentage change in demand for a one-percent change in income, and the price elasticity does the same for price; both are recovered as coefficients in econometric demand models, most simply a log-linear regression where the coefficients read directly as elasticities. Geoffrey Crouch's mid-1990s surveys of the international tourism demand literature consolidated decades of such estimates, showing that tourism is typically income-elastic — a luxury that grows faster than income — and price-sensitive, with values that vary systematically across markets and methods. Later meta-analyses, such as Peng, Song, Crouch, and Witt's, quantified that variation across hundreds of studies.