Migration-fertility trade-off in low fertility populations

Jow-Ching Tu, Hong Kong University of Science and Technology
Xin Yuan, Nankai University

Fertility is below replacement level in many countries, and population growth is expected to turn into decline in the coming decades. Increasing life expectancy will accentuate the concomitant aging. Migration has been seen as a possible means to decelerate aging. We introduce a stable open population model in which net-migration is proportional to births. In this case the migration-fertility trade-off can be studied with particular ease. We show that while migration can increase the growth rate, which tends to make the age-distribution younger, it also has an opposite effect due to its typical age pattern. We capture the effect of the age-pattern of net-migration in a migration survivor function. The effect of net-migration on growth is quantified. It is shown that some countries already have a level of migration that will lead to stationary. For others with asymptotically declining population migration still provides opportunities for slowing down aging.