Non-economic push factors include persecution (religious and otherwise), frequent abuse, bullying, oppression, ethnic cleansing and even genocide, and risks to civilians during war. Political motives traditionally motivate refugee flows - to escape dictatorship for instance.
Some migration is for personal reasons, based on a relationship (e.g. to be with family or a partner), such as in family reunification or transnational marriage. In a few cases, an individual may wish to emigrate to a new country in a form of transferred patriotism. Evasion of criminal justice (e.g. avoiding arrest) is a (mostly negative) personal motivation. This type of emigration and immigration is not normally legal, if a crime is internationally recognized, although criminals may disguise their identities or find other loopholes to evade detection. There have been cases, for example, of those who might be guilty of war crimes disguising themselves as victims of war or conflict and then pursuing asylum in a different country.
Barriers to immigration come not only in legal form; natural barriers to immigration can also be very powerful. Immigrants when leaving their country also leave everything familiar: their family, friends, support network, and culture. They also need to liquidate their assets often at a large cost, and incur the expense of moving. When they arrive in a new country this is often with many uncertainties including finding work, where to live, new laws, new cultural norms, language or accent issues, possible racism and other exclusionary behavior towards them and their family. These barriers act to limit international migration: scenarios where populations move en masse to other continents, creating huge population surges, and their associated strain on infrastructure and services, ignore these inherent limits on migration.
General arguments
The main arguments cited in support of immigration are economic arguments, such as a free labor market, and cultural arguments appealing to the value of cultural diversity. Some groups also support immigration as a device to boost small population numbers, like in New Zealand and Canada, or, like in Europe, to reverse demographic aging trends.
Support for fully open borders is limited to a minority. Some free-market libertarians believe that a free global labor market with no restrictions on immigration would, in the long run, boost global prosperity. There are also groups which oppose border controls on ideological grounds - believing that people from poor countries should be allowed to enter rich countries, to benefit from their higher standards of living. Others are advocates of world government and wish to eliminate or severely limit the power of nation-states. This includes the nation-state's ability to grant and deny individuals entry across borders, which advocates of world government generally view as arbitrary and unfair distinctions made on what should be one planet earth, thus eliminating diversity and competition among states.
Economic arguments
Countries like New Zealand, which has experimented with both qualifications- and job-offer-based entry systems, have reported that under the latter system (where much weight is put on the immigrant already having a job offer), the immigrants actually show a much lower uptake of government benefits than the normal population. Under a mostly qualification-based system, many highly trained doctors and engineers had instead been reduced to driving taxis.
1.5. Opposing arguments
The main anti-immigration themes include costs of immigration (potential free-riding on existing welfare systems), labor competition; environmental issues (the impact of population growth); national security (concerns of insular immigrant groups & terrorism against the host country); lack of coordination & cooperation among citizens (differences of language, conventions, culture); and the loss of national identity and culture (including the nature of the nation-state itself).
Health arguments
Immigration from areas of high incidence is thought to have fueled the resurgence of tuberculosis (TB), chagas, hepatitis, and leprosy in areas of low incidence. To reduce the risk of diseases in low-incidence areas, the main countermeasure has been the screening of immigrants on arrival. According to CDC, TB cases among foreign-born individuals remain disproportionately high, at nearly nine times the rate of U.S.-born persons. In 2003, nearly 26 percent of foreign-born TB patients in the United States were from Mexico. Another third of the foreign-born cases were among those from the Philippines, Vietnam, India and China, the CDC report said.
The history of HIV/AIDS in the United States began in about 1969, when HIV likely entered the United States through a single infected immigrant from Haiti.
Economic arguments
Economic needs-driven immigration is opposed by labor-market protectionists, often arguing from economic nationalism. The core of their arguments is that a nation's jobs are the 'property' of that nation, and that allowing foreigners to take them is equivalent to a loss of that property. They may also criticize immigration of this type as a form of corporate welfare, where business is indirectly subsidized by government expenditure to promote the immigration and the assimilation of the immigrants. A more common criticism is that the immigrant employees are almost always paid less than a non-immigrant worker in the same job, and that the immigration depresses wages, especially as immigrants are usually not unionized. Other groups feel that the focus should be not on immigration control, but on equal rights for the immigrants, to avoid their exploitation.
Nationalistic arguments
Non-economic opposition to immigration is closely associated with nationalism, in Europe a 'nationalist party' is almost a synonym for 'anti-immigration party'.
The primary argument of some nationalist opponents in Europe is that immigrants simply do not belong in a nation-state which is by definition intended for another ethnic group. France, therefore, is for the French, Germany is for the Germans, and so on. Immigration is seen as altering the ethnic and cultural composition of the national population, and consequently the national character. From a nationalist perspective, high-volume immigration potentially distorts or dilutes their national culture more than is desired or even necessary. Germany, for example, was indeed intended as a state for Germans: the state's policy of mass immigration was not foreseen by the 19th-century nationalist movements. Immigration has forced Germany and other western European states to re-examine their national identity: part of the population is not prepared to redefine it to include immigrants. It is this type of opposition to immigration which generated support for anti-immigration parties such as Vlaams Belang in Belgium, the British National Party in Britain, the Lega Nord in Italy, the Front National in France, and the Lijst Pim Fortuyn in the Netherlands.
One of the responses of nation-states to mass immigration is to promote the cultural assimilation of immigrants into the national community, and their integration into the political, social, and economic structures. In Europe, where nation-states have a tradition of national unification by cultural and linguistic policies, variants of these policies have been proposed to accelerate the assimilation of immigrants. The introduction of citizenship tests for immigrants is the most visible form of state-promoted assimilation. The test usually include some form of language exam, and some countries have reintroduced forms of language prohibition.
Environmentalist arguments
Most European countries do not have the high population growth of the United States, and some experience population decline. In such circumstances, the effect of immigration is to reduce decline, or delay its onset, rather than substantially increase the population. The Republic of Ireland is one of the only EU countries comparable to the United States in this respect, since large-scale immigration contributed to substantial population growth. Spain has also witnessed a recent boost in population due to high immigration.
