Megacities, Migration and Forced Displacement

Migration is the movement of people involving a change of permanent residence. It reshapes population distribution far faster than births and deaths can, and it is closely tied to the rise of megacities—urban agglomerations with more than ten million inhabitants. In 1950 there were only a couple of such cities; today there are more than thirty, including Tokyo, Delhi, Shanghai, São Paulo, Mexico City, Cairo, and Lagos, and most are in the developing world.

Types of migration

Geographers classify migration along several axes. Internal migration takes place within a country, while international migration crosses borders. Movement can be permanent or temporary, voluntary or forced. The most important distinction for this topic is between voluntary migration, where people choose to move mainly