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	Vacancy Chain Analysis	Gravity Model of Migration
分野	Human Geography	Human Geography
系統	Process / pipeline	Regression model
提唱年	1970	1946
提唱者	Harrison C. White	George Kingsley Zipf (formalized); analogy to Newton's law of gravitation
種類	System model of mobility driven by the movement of vacancies through linked units	Spatial-interaction regression model for migration flows
原典	White, H. C. (1970). Chains of Opportunity: System Models of Mobility in Organizations. Harvard University Press, Cambridge, MA. ISBN: 9780674080652	Zipf, G. K. (1946). The P1 P2 / D hypothesis: On the intercity movement of persons. American Sociological Review, 11(6), 677–686.
別名	Vacancy Chain Model, Chains of Opportunity, Vacancy Transfer Analysis, Vacancy Chain Mobility Model	Migration Gravity Model, Demographic Gravity Model, Zipf P1P2/D Model, Gravity Model of Spatial Interaction (Migration)
関連	4	4
概要	Vacancy chain analysis is a system model of mobility, introduced by Harrison White in his 1970 book Chains of Opportunity, that follows opportunities rather than people. When a unit such as a house or a job is freed and filled by someone who in turn vacates another unit, a chain of moves cascades through the system until it ends with a new entrant or a unit leaving the stock. By treating vacancies as the things that move — through an absorbing Markov chain — the framework explains how a single new dwelling or retirement can ripple into many household relocations or promotions.	The gravity model of migration explains the volume of movement between two places as proportional to the product of their populations (masses) and inversely proportional to the distance separating them, by direct analogy to Newton's law of universal gravitation. Formalized for intercity movement by George Kingsley Zipf in 1946 and embedded in regional science by Walter Isard, it is the workhorse model of human geography for predicting migration, commuting, and other spatial-interaction flows.