手法を比較

	Intervening Obstacles Analysis	Intervening Opportunities Model
分野	Migration Studies	Migration Studies
系統	Process / pipeline	Regression model
提唱年	1966	1940
提唱者	Everett S. Lee	Samuel A. Stouffer
種類	Analytical framework for migration barriers and their selectivity	Spatial-interaction model of migration volume
原典	Lee, E. S. (1966). A Theory of Migration. Demography, 3(1), 47-57.	Stouffer, S. A. (1940). Intervening Opportunities: A Theory Relating Mobility and Distance. American Sociological Review, 5(6), 845-867.
別名	Migration Barriers Analysis, Obstacle Selectivity Analysis, Lee Intervening Obstacles Framework, Migration Friction Analysis	Stouffer Intervening Opportunities, Opportunity-Based Migration Model, Law of Intervening Opportunities
関連	3	3
概要	Intervening obstacles analysis isolates and studies the third term in Everett Lee's 1966 theory of migration: the set of barriers that stand between an area of origin and an area of destination and that must be surmounted before any move, however attractive, can take place. Lee distinguished these obstacles — distance, the cost of transport, legal restrictions, borders, and physical frontiers — from the push and pull factors of the places themselves, arguing that they impose a threshold the net attraction must clear. Crucially, obstacles do more than reduce volume: because the ability and willingness to overcome a given barrier vary across individuals, obstacles act as a filter that selects who migrates, shaping the composition of the flow as well as its size. Massey and colleagues' 1993 appraisal situated this barrier logic within migration theory and connected it to policy levers such as border enforcement and visa regimes that deliberately raise obstacles. The analysis proceeds by enumerating and weighting the relevant obstacles, modeling the threshold they create, and assessing the resulting selectivity. It has become especially salient as states use legal and physical barriers to manage international migration.	The intervening opportunities model, introduced by Samuel Stouffer in 1940, explains the volume of migration between two places not by the physical distance separating them but by the number of opportunities available at the destination relative to the opportunities a migrant would encounter along the way. Its central claim is provocative: there is no necessary relationship between mobility and distance. Distance only matters because crossing more of it usually means passing more chances to stop. Formally, the number of people moving a given distance is directly proportional to the number of opportunities at that distance and inversely proportional to the number of intervening opportunities. Stouffer revised the model in 1960 to add 'competing migrants' — rivals converging on the same destination from other origins — giving spatial-interaction analysis an alternative to the gravity model that is grounded in opportunity structure rather than mass and distance.