Docquier , Frédéric, and Joël Machado. “Income, Population and Migration Flows in the 21st Century - A Societal Challenge for Europe”. Studia Oeconomica Posnaniensia 2, no. 12 (June 30, 2026): 162–185. Accessed September 3, 2026. https://journals.ue.poznan.pl/soep/article/view/3782.