The ongoing decline of Europe’s population, the explosion of Africa’s, major changes in migratory flows, significant variation of reproduction levels across countries and ethnic groups, and the dizzying growth of large urban aggregates have all appeared over the last hundred years. They modify and upset relations between states and regions of the world and influence political choices, with variable and even unpredictable force and speed. But geodemography, a wide-ranging and innovative perspective, can help understand these trends. Using a broad repertoire of exemplary cases drawn from recent world history, this book illustrates this novel approach, proving that it is a valuable tool for learning more about relations among countries and their future.