Characteristics of population migration before World War II

International population migration:1.1Before the 9th century, the overall characteristics of international population migration were group and mass migration. 2. After the Second World War, international population migration has shown new characteristics: population flows from developing countries to developed countries; There are few settled residents, and the short-term floating population increases. Reasons: (If you want economic reasons, I will only say economic reasons, but ... intentional reasons are not the most important ~) The purpose of population migration is to seek more "opportunities" to improve material living conditions, obtain better economic treatment and improve personal and family life. Thanks ~!