手法を比較

	Population Potential Model	Gravity Model of Migration
分野	Human Geography	Human Geography
系統	Process / pipeline	Regression model
提唱年	1947	1946
提唱者	John Q. Stewart	George Kingsley Zipf (formalized); analogy to Newton's law of gravitation
種類	Social-physics measure of the cumulative influence of population at a location	Spatial-interaction regression model for migration flows
原典	Stewart, J. Q. (1947). Empirical mathematical rules concerning the distribution and equilibrium of population. Geographical Review, 37(3), 461–485.	Zipf, G. K. (1946). The P1 P2 / D hypothesis: On the intercity movement of persons. American Sociological Review, 11(6), 677–686.
別名	Potential of Population, Market Potential Model, Demographic Potential, Stewart Potential	Migration Gravity Model, Demographic Gravity Model, Zipf P1P2/D Model, Gravity Model of Spatial Interaction (Migration)
関連	4	4
概要	The population potential model measures the cumulative influence that all of a region's population exerts on a given point, weighting each place's population inversely by its distance. Introduced by the astronomer-turned-social-scientist John Q. Stewart in 1947 as part of his 'social physics', it borrows the gravitational-potential analogy from physics: every population mass contributes potential at a point in proportion to its size and in inverse proportion to its distance. Summed across all places, the result is a smooth potential surface that maps relative accessibility, market reach, and demographic pressure.	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.