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Force, chain and mass migration

A voluntary movement of adventurous pioneers or of dissident individuals or groups is called a free migration. Although few people are involved, they set an example for others. As the migrants write and visit home, they may induce relatives and friends to follow them. Then, as new migrants repeat this process in turn, a chain migration of thousands of people may result.
Nevertheless, chain migration may lead to mass migration. This occurs when communication between two regions becomes so intensive that a tradition of migration is created and the volume of the movement grows very large. Mass migration can be regarded as a form of collective behavior, in which individual motivations are less significant than the established pattern.