The world population has undergone an unprecedented demographic transition (shift from high birth/death rates to low birth/death rates), with total fertility rates falling from 6.0 births per woman in the post-WWII era to 2.4 in 2024, barely above the replacement rate (2.1 births per woman needed to maintain population). This chapter examines the economic implications of population decline in developed nations, the emergence of a global labor shortage (insufficient workers for available jobs), and the challenges of international migration as a solution. Through analysis of specific country cases—Turkey-Germany, Mexico-United States, and Guatemala’s migration corridor—we demonstrate that no single country can provide sufficient young migrants to resolve the demographic imbalances of aging rich nations. The chapter concludes with policy recommendations for phased migration (gradual, managed population movement) and improved assimilation (integration of immigrants into host societies) processes.