Immigration is the movement of people into a destination country to which they are not native or do not possess its citizenship in order to settle or reside there, especially as permanent residents or naturalized citizens, or to take-up employment as a migrant worker or temporarily as a foreign worker.When people during their migration cross national borders, they are from the perspective of the country which they enter, called migrants or immigrants (from Latin: migrare, wanderer). From the perspective of the country which they leave, they are called emigrant or outmigrant. Sociology designates immigration usually as migration (as well as emigration accordingly outward migration). Immigrants are motivated to leave their former countries of citizenship or habitual residence for a variety of reasons, including a lack of local access to resources, a desire for economic prosperity, to find or engage in paid work, to better their standard of living, family reunification, retirement, climate or environmentally induced migration, exile, escape from prejudice, conflict or natural disaster, or simply the wish to change one's quality of life. Commuters, tourists and other short-term stays in a destination country do not fall under the definition of immigration or migration, seasonal labour immigration is sometimes included.In 2013 the United Nations estimated that there were 231,522,215 immigrants in the world (apx. 3.25% of the global population).