The development and change of population is restricted by social and economic development. As an aspect of world population development, international population migration also reflects global political and economic changes.
Before the 20th century, human economic development mainly depended on the increase of labor force. In line with this, the purpose of international population migration is mainly to develop "virgin land". For example, after/kloc-discovered the new continent in the 0/5th century, Spain, Portugal, the Netherlands, Britain and France began the colonial policy of exploring America. They brought two kinds of immigrants: one came from Europe and moved to the new world for the purpose of plundering gold and silver treasures and making a fortune; Another kind of immigrants come from Africa. They were slaves sold to America by these colonists. For another example, from the19th century to the first half of the 20th century before World War I, European countries, under the pressure of their own population growth and the pull of North America's urgently needed labor force, formed an immigration tide to the United States.
The two world wars blocked the normal international population migration, but as soon as the war ended, the international population migration entered a new historical period and presented some new characteristics.
First of all, political international migration has increased dramatically. After the war, Europe redrawed its national boundaries, which made the countries in Eastern Europe enter and leave each other because of the changes in national boundaries. India and Pakistan are divided. It has formed the largest international migration of population in Asia: in independent African countries, the original colonists were forced to repatriate their populations.
Second, the flow of international migration has undergone tremendous changes. The demand for labor in the United States has decreased, and a large number of Europeans have returned home from colonies. With the rapid development of European economy and the reduction of population pressure after the war, the number of people who moved out decreased, and the region changed from a place where people moved out to a place where people moved in.
Third, the United States is still the main place of immigration, but the source structure of immigrants has changed. European immigration has decreased, and Latin America has become the main source of immigration. After 1970s, the number of immigrants in Asia surpassed that in Europe.
After the war, the phenomenon of international population migration changed from capitalist countries to backward colonies to poor countries to rich countries, which had different effects on developed countries and developing China countries.
Because the population growth is slow. For developed countries with a serious aging population, immigrants make up for the shortage of their labor force. Immigrants with specialized skills not only bring scientific knowledge and production technology from other countries, but also save education expenses for immigrant countries. For developing countries whose population growth rate is still high, although the emigration of population has eased the pressure on their own population, because these people are not ordinary laborers, but scientific and technological personnel, professionals and talents, a large number of high-quality laborers created by training fees are used abroad, which is undoubtedly the biggest loss for developing countries.
With the development of large industries, economic growth no longer depends mainly on the expansion of labor-intensive industries, and science and technology become the primary productive force. International competition is the competition of talents in a specific environment. Therefore, how to stop the phenomenon of "brain drain" in developing countries caused by various factors is the main problem in the current international population migration research.