Σύγκριση μεθόδων

	Place-to-Place Migration Model	Gravity Model of Migration
Πεδίο	Migration Studies	Human Geography
Οικογένεια	Regression model	Regression model
Έτος προέλευσης	1966	1946
Δημιουργός	Ira S. Lowry; (gravity antecedent: George K. Zipf)	George Kingsley Zipf (formalized); analogy to Newton's law of gravitation
Τύπος	Econometric origin-destination flow model	Spatial-interaction regression model for migration flows
Θεμελιώδης πηγή	Lowry, I. S. (1966). Migration and Metropolitan Growth: Two Analytical Models. Chandler Publishing, San Francisco. ISBN: 9780810200135	Zipf, G. K. (1946). The P1 P2 / D hypothesis: On the intercity movement of persons. American Sociological Review, 11(6), 677–686.
Εναλλακτικές ονομασίες	Origin-Destination Migration Model, Lowry Migration Model, Econometric Gross-Flow Model, Modified Gravity Migration Model	Migration Gravity Model, Demographic Gravity Model, Zipf P1P2/D Model, Gravity Model of Spatial Interaction (Migration)
Συναφείς	3	4
Σύνοψη	The place-to-place migration model explains and predicts the gross number of people moving from each origin region to each destination region as a function of conditions at both ends and the distance between them. It descends from the gravity analogy popularized by George Zipf in 1946, in which movement between two cities rises with the product of their populations and falls with the distance separating them, but it adds behavioral economic content. Ira Lowry's 1966 formulation is the canonical example: he modeled interregional migration as driven by relative labor-market conditions — wages, unemployment, and the size of the labor force at origin and destination — modified by distance, and estimated the relationship econometrically from observed flows. Cast in log-linear or, in modern practice, Poisson form, the model recovers interpretable elasticities showing how flows respond to a wage gap or an unemployment differential, and it can reproduce or forecast the entire origin-destination matrix. It bridges the descriptive gravity tradition and explicit regression-based migration econometrics, and remains a workhorse for analyzing why people move where they do.	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.