Dissecting Network Externalities

Existing migrant networks play an important role in explaining the size and structure of immigration flows. They affect the net benefits of migration by reduc-ing assimilation costs (’self-selection channel’) and by lowering legal entry barriers through family reunification programs (’immigration policy channel’). This paper presents an identification strategy allowing to disentangle the relative importance of these two channels. Then, it provides an empirical analysis based on US immi-gration data by metropolitan area and country of origin. First, we show that the overall network externality is strong: the elasticity of migration flows to network size is around one. Second, only a quarter of this elasticity is accounted for by the policy channel. Third, the policy channel was stronger in the 1990s than in the 1980s as the family reunification programs became more effective with growing diasporas. Fourth, the overall diaspora effect and the policy channel are more important for low-skilled migrants. JEL Classification: F22, O1