Supply factors: demography, economy and skills

International migration is difficult to measure. Although more databases exist today than ever before, uncertainties remain: sources, deriving mainly from national governments, are not always comparable and a relevant part of the phenomenon is, and tends to remain, undocumented. Available data indicate that international migration has been slowly but steadily increasing over the past few decades, despite growing attempts to curb it on part of the destination countries. Currently, little less than 4% of the world population is made of migrants, defined as people living in a country other than that of birth. Push factors will remain strong in the next 30 to 40 years, population pressure being perhaps the single most important cause, as a direct consequence of the bulk of young adults that is forming in low-income countries, and especially in Sub-Saharan Africa. International migration will likely remain at least as high as in the past twenty years.