Intervening Obstacles Analysis

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.