Immigration is the act of moving to or settling in another country or region, temporarily or permanently. An immigrant is usually someone who intends to reside permanently, and not a casual visitor or traveler. Immigration means "in-migration" into a country, and is the reverse of emigration, or "out-migration." The long term and/or permanent movement of human population in general, whether into, out of, or within countries (or before the existence of recognized countries) is regarded as migration.

Why people immigrate

People immigrate for the following reasons:

professional,
political,
economic
persecution
sentimental (i.e., the desire to settle in a country due personal preference; family reunification).

Economic reasons for immigration.

Much immigration occurs for economic reasons. Wage rates vary greatly between different countries; individuals of third world countries in particular can have far higher standards of living in developed countries than in their originating countries. The economic pressure to migrate can be so high that when legal means are restricted, people may immigrate regardless of their legal status.

National reactions to immigration.

Throughout the world, immigration is a controversial issue. All developed nations put restrictions on how many people can immigrate to them. These are usually justified on economic grounds with worries that many poor workers would lower wages and the nation's standard of living. Sometimes the justification for limiting immigration is cultural. The latter is heard most strongly in homogenous old world (European) nations where citizenship was long tied to a person having deep historical roots in the country. Western European nations, Japan, and other countries have long been deeply concerned about their national culture being subsumed. This concern can be especially high when the immigrants are of differing race or religion than the majority.

European immigration.

Immigration into European countries has a long tradition, though until the 1970s and 1980s the levels were relatively modest. Recent increases in immigration have led to the development of political parties in Europe which are almost solely concerned with limiting immigration.

Countries encourage immigration.

Only five countries in the world "actively encourage" large numbers of immigrants: The United States, Israel, Canada, New Zealand, and Australia. These nations still restrict the numbers of people allowed to immigrate, but in these countries, population growth is almost entirely due to the relatively large level of immigration. Many other countries permit immigration in particular circumstances, e.g., to fill jobs where a skill is not available locally, for wealthy investors or business leaders, in cases of marriage, multiple citizenship or asylum, or under multilateral agreements such as within the European Union or between New Zealand and Australia.

Differing perspectives on immigration

Some free-market libertarians believe that a free global labor market with no restrictions on immigration would, in the long run, boost global prosperity. Likewise, there are anarchists on the left who believe national borders are not legitimate to begin with. On the opposite side of the issue, among the immigration educationists there are nationalists who propose militarizing borders, protectionists who prefer closed labor markets, and xenophobes who fear the presence of foreigners. Most people believe that some limits on immigration are necessary. The disagreement is over the numbers, policies, and implementation. Those who support more restricted immigration believe that the current levels of immigration are too high, and serve to depress wages and circumvent unionization, and contribute to unsustainable levels of population growth. Others disagree, believing that overly restrictive immigration policies and practices would not address the economic demand for work emanating from wealthier countries, would not harm the safety or cohesiveness of the country, and would endanger the lives of legitimate refugees.

Immigration is a controversial topic.

Immigration has become an increasingly controversial topic among environmental activists in recent years, especially within the Sierra Club in the United States. Some environmentalists concerned with overpopulation favor limiting immigration as a means of isolating human population growth, while others argue that overpopulation and environmental degradation are global problems that should be addressed by other methods.