What changes have taken place in the source of international population who immigrated to the United States before and after World War II?

American population migration after World War II;

From the end of 15 to the beginning of 16, the mainstream of population migration was from the "old continent" to the "new continent". The immigrant areas are Asia, Europe and Africa, and the immigrant areas are North and South America, Southeast Asia and Oceania. Among them, the brutal sale of African slaves by European colonists is the largest and longest-lasting forced international migration in human history.

After the Second World War, the new feature of international population migration is that the proportion of permanent immigrants has decreased, and the forms of migration tend to be diversified, which is manifested in the sharp increase of political international population migration and major changes in its flow direction. Europe and America have become immigrant areas, and the emigration areas are Asia and Latin America. The emergence of emerging cities and emerging industries has triggered a large number of population migration.