Immigration is the movement of people into a country to which they are not native in order to settle there, especially as permanent residents or future citizens. Immigrants are motivated to leave their native countries for a variety of reasons, including a desire for economic prosperity, political issues, family re-unification, escaping conflict or natural disaster, or simply the wish to change one's surroundings. In 2013 the United Nations estimated that there were 231,522,215 immigrants in the world. Immigration is a highly debated and controversial topic in today's global community.