What is the history of migration in terms of the long span of human societies? How has migration changed in terms of the demographic transition? What factors have impacted it? How is it currently working, briefly, to create the population growth/numbers/age, as we see it now?
Today, data pulled by the International Organization for Migration shows that there are four different migrational patterns. The greatest majority of emigrants--over 82 million (36%)--are coming from developing countries in the south and moving to other developing countries in the south. For example, emigrants may come from Indonesia and migrate to Saudi Arabia or from Nicaragua and migrate to Costa Rica. We call this the South-South pattern. About 81% of South-South migrants are refugees. The second-largest group of emigrants--just under 82 million (35%)--are coming from either developing or middle-income countries in the south and moving to high-income countries in the north, which we call the South-North pattern. The third migrational pattern is the North-North pattern, which consists of a smaller population of people--54 million (23%)--moving from the north to other countries of the north, such as from the U.S. to Canada. The smallest migrational pattern, the North-South pattern, consists of 14 million people (6%) moving from high-income countries in the north, such as from Japan, to developing countries, such as to Thailand ("Migrant Well-Being and Development"; Population Reference Bureau, "The Global Challenge of Managing Migration").
Other than in the case of South-South refugees, the predominate reason for migration is economic. Data from the United Nations and the World Bank, analyzed by the Pew Research Center, shows that the predominant global migration trend is a rise in migrants to "high-income countries" ("Chapter 1: Overview," Changing Patterns of Global Migration and Remittances). While the largest percentage of migrants are moving to the U.S., migrants are also moving to other high-income countries, such as Russia, Germany, the United Kingdom, France, Canada, Australia, and even the United Arabia Emirates and Saudi Arabia (World Bank, "Migration Remittances: Top Countries"). Most of these immigrants have come from "middle-income countries," such as India, Mexico, China, Ukraine, Pakistan, and many others (World Bank).
Though the U.S. is the top destination country for migration, the total immigrant population is much lower than in other destination countries. Immigrants make up only 14% of the total population in the U.S., whereas immigrants make up 21% percent of the population in Canada, and 28% in Australia. In addition, more than half of all immigrants coming to the U.S. are from Latin America and the Caribbean (Pew Research Center).
For most of the migratory patterns, a greater percentage of migrants are men. The one exception is the North-North pattern, in which a higher percentage of women are migrating. In addition, the largest percentage of immigrants living in either the north or south are 65 years or older. One might presume that more elderly are migrating in pursuit of greater quality of life. The second-largest percentage of migrants are in the working-age group, between 30 and 44 years of age. The greatest percentage of migrants are also low-skilled workers (International Organization for Migration).