International migration (1945-1957)

Since the end of the Second World War, migratory movements on a quite unprecedented scale have taken place throughout the world. Millions of people have been driven from their homes and the population structure of entire countries radically altered. Political upheavals involving the redrawing of frontiers, transfers of sovereignty and changes of regime have forced entire populations into exile and caused mass movements far in excess of those normally resulting from supply and demand on the world employment market. Thus a characteristic feature of migratory currents during this period, apart from their size, has been the existence of political, as distinguished from economic, migration movements.
This fundamental distinction, on which the over-all plan of this study is based, is not simply a matter of form. It stems from a basic difference between the two phenomena, in cause and effect as well as in pattern. The political movements were the product of exceptional circumstances and in most cases were sweeping and precipitate, their momentum quickly spent. Economic migration currents, on the other hand, have tended to flow fairly steadily in fixed channels. Whereas individual choice has played only a very small part in the former, which were usually the result of threats or coercion, it has been a decisive factor in the latter, which were the voluntary, if not always spontaneous, expression of a desire for better conditions. Moreover, the former have usually affected entire groups of human beings who were uprooted for good, whereas the latter have largely involved young adults, often only temporarily.