Definition
Internal migration is the movement of people from one part of a country to another, crossing regional or administrative boundaries but not national ones.
Demographers distinguish it from international migration (across state borders) because the two have different legal regimes, different barriers to entry, and different statistical treatments — internal migrants do not need passports, are usually counted in standard census instruments, and face no formal exclusion. But the scale of internal migration in many countries dwarfs international flows: the U.S. Great Migration moved roughly six million people, and twentieth-century rural-to-urban migration in China moved several hundred million.
Why it matters
How it works
Most internal migrations share a structural pattern. A push factor at the origin — failing agriculture, political repression, environmental collapse — combines with a pull at the destination — industrial wages, new opportunity, relative freedom. A pioneer cohort moves first, often selectively (younger, more educated, more able). A chain forms as the pioneers send back information and money. A migration stream consolidates along specific corridors: rail lines, highways, river routes. After some decades, the flow tapers — either because the origin empties out, the destination saturates, or the conditions equalize.
Three canonical examples illustrate the range. The U.S. Great Migration (1915–1970) moved six million Black Americans from the rural South to Northern and Western cities under the push of Jim Crow segregation and the pull of industrial labor demand. China's rural-to-urban migration (1980–present) has moved an estimated 300 million people from interior agricultural villages to coastal manufacturing cities — pulled by export-industry wages, throttled and channeled by the hukou household-registration system. The Trekboers of nineteenth-century South Africa migrated north from the Cape into the interior under the pressure of British colonial administration, eventually founding the Boer republics.
What internal migrations share with international ones is everything social — kin networks, chain dynamics, remittance flows, identity preservation, second-generation outcomes. What they avoid are the legal and border-enforcement frictions, which makes them in some ways purer laboratories for studying migration mechanics.