Tracing International Migration in Projections of Income and Inequality Across the Shared Socioeconomic Pathways

The Shared Socioeconomic Pathways (SSPs) represent five narratives of future develop-ment used for climate change research. They include quantified projections of socioeco-nomic variables such as population, income levels, inequalities, and emissions over thetwenty-first century. The SSP’s population projections embody explicit, pathway-specificinternational migration assumptions, which are only implicit in the projections of othervariables. In this contribution, we explicitly quantify the effects of international migrationon income levels and income inequality across and within countries by comparing theoriginal SSP projections to scenarios of zero migration. Income projections withoutmigration are obtained by removing two effects of migration on income dynamics:changes in population size and remittances sent to origin countries. We base ourremittance estimates on migrant stocks derived from bilateral migration flow estimatesobtained from a gravity model. We find that, on average, migration tends to make theworld richer in all SSP narratives. The nature of migration and remittance corridors isshaped by the specific scenario of future development considered. Depending on theparticular SSP narrative and world region considered, the effects of migration on incomecan be substantial, ranging from−5 to +21% at the continental level. We show thatmigration tends to decrease income inequality across countries and within country inmost destination countries but does not affect within-country inequality in origin coun-tries. This new set of projections is consistent with the interdisciplinary framework of theSSPs, which makes it particularly useful for assessing global climate and sustainabledevelopment policy options.