Immigration is the introduction of new people into a habitat or population. It is a biological concept and is important in population ecology, differentiated from emigration and migration.
The International Organization for Migration (IOM) said there are more than 200 million migrants around the world today. Europe hosted the largest number of immigrants, with 70.6 million people in 2005, the latest year for which figures are available. North America, with over 45.1 million immigrants, is second, followed by Asia, which hosts nearly 25.3 million. Most of today’s migrant workers come from Asia. The United Nations estimates that there are 214 million migrants across the globe, an increase of about 37% in two decades.
One theory of immigration distinguishes between Push and Pull. Push factors refer primarily to the motive for emigration from the country of origin. In the case of economic migration (usually labour migration), differentials in wage rates are prominent. If the value of wages in the new country surpasses the value of wages in one’s native country, he or she may choose to migrate as long as the costs are not too high. Particularly in the 19th century, economic expansion of the U.S. increased immigrant flow, and in effect, nearly 20% of the population was foreign born versus today’s values of 10%, making up a significant amount of the labor force. Poor individuals from less developed countries can have far higher standards of living in developed countries than in their originating countries. The cost of emigration, which includes both the explicit costs, the ticket price, and the implicit cost, lost work time and loss of community ties, also play a major role in the pull of emigrants away from their native country.