Projection of net migration using a gravity model

Countries and demographers differ regarding the definition, estimation, and projection of international migrant stocks and migration flows. Despite these difficulties, the United Nations Population Division prepares, every two years, estimates, referring to past quantities, and projections, referring to future quantities, of net migration (immigration minus emigration) for all countries and regions of the world. We compare two examples taken from the World Population Prospects: The 2010 Revision (United Nations, Department of Economic and Social Affairs, Population Division, 2011), with alternative projections of net migration based on gravity-type models for migration flows (Cohen et al., 2008 and Kim and Cohen, 2010). The two examples refer to (a) net migration from less developed regions to more developed regions and (b) net migration from the rest of the world, excluding the United States of America, to the United States of America. In both examples, the UN projections assume net migration declines to 0 by 2100. By contrast, in the gravity-model projections, net migration rises smoothly to a plateau about twice as high as present estimates of net migration; net migration ceases to increase as the populations of origin and destination countries stabilize.