The Determinants of International Migration: Theory

The economic theory of external migration is concerned with three questions – why migrate, who migrates, and what are the consequences for source and destination countries? This chapter deals with the why question. It surveys the theoretical literature on the economic determinants of international migration. This literature is very small and relatively young, but has its roots in the \much older theory of internal, or regional, migration. The standard model used implies that the immigration rate depends upon international differences in the returns to factor supply, controlling for migration costs, skill levels, income inequality, and immigration policies. We also discuss other models that focus on how the immigration decision is influenced by family considerations, the option value of waiting, and feelings of relative deprivation. There is still a big gap between theory and empirical work on the determinants of emigration, and \much needs to be done on the theoretical side of this literature to bridge that gap. The greatest challenge to migration theorists is the organization of all hypothetically relevant factors into one coherent theoretical framework that will specify their interaction with each other in empirically testable form and thereby serve as a guide to future research.(United Nations, 1973)