Tracing international migration in projections of income and inequality across the Shared Socioeconomic Pathways

The Shared Socioeconomic Pathways (SSPs) represent five narratives of future development used for climate change research. They include quantified projections of socioeconomic variables such as population, income levels, inequalities, and emissions over the twenty-first century. The SSP’s population projections embody explicit, pathway-specific international migration assumptions, which are only implicit in the projections of other variables. In this contribution, we explicitly quantify the effects of international migration on income levels and income inequality across and within countries by comparing the original SSP projections to scenarios of zero migration. Income projections without migration are obtained by removing two effects of migration on income dynamics: changes in population size and remittances sent to origin countries. We base our remittance estimates on migrant stocks derived from bilateral migration flow estimates obtained from a gravity model. We find that, on average, migration tends to make the world richer in all SSP narratives. The nature of migration and remittance corridors is shaped by the specific scenario of future development considered. Depending on the particular SSP narrative and world region considered, the effects of migration on income can be substantial, ranging from −5 to +21% at the continental level. We show that migration tends to decrease income inequality across countries and within country in most destination countries but does not affect within-country inequality in origin countries. This new set of projections is consistent with the interdisciplinary framework of the SSPs, which makes it particularly useful for assessing global climate and sustainable development policy options.