The transfer of people from a nation-state to another country, where it is not a citizen. Immigration refers to the migration to permanent residence by immigrants, while tourists and migrants for short periods of time are not considered immigrants. However, the migration of seasonal workers (generally for periods of less than one year) is often considered a form of immigration. The UN estimates that there were around 190 million international immigrants in 2005, around 3% of the world's population. The rest lives in their home country or successor country.
