Innovations in International Migration for Use in Global Population Projections

Guy J. Abel, Wittgenstein Centre (IIASA, VID/ÖAW, WU)
Nikola Sander, Vienna Institute of Demography

Advances in projecting international migration have been hindered by a lack of adequate data. Consequently, international projection-making agencies commonly use simplistic assumptions of net-migration measures derived as residuals from demographic accounting. However, past net migration can be often volatile and are known to introduce inaccuracies when projecting populations (Rogers, 1990). This paper presents a set of global population projections to 2050, focusing on alternative international migration assumptions. Using a first-of-a-kind set of estimated quinquennial bilateral migration flows developed by Abel (2013) in a multiregional cohort-component projection model, alternative future migration trends are explored based on a set of ‘what-if?’ scenarios. Scenarios combine expert-based assumptions about fertility, mortality and migration developed for the 2012 edition of the IIASA-Oxford global population projections. Our results highlight differences in the future level and distribution of populations around the globe between a constant-rates, a convergence to zero-net, a zero flows and two ‘what-if’ scenarios.