Immigration is the movement of individuals into a population or area. It is the counterpart to emigration. When people move from one country to another, they are emigrants from the place they left and immigrants to the place they arrive. Immigration adds to a population. It also changes its composition, bringing new languages, skills, and cultural practices. Demographers track immigration because it affects population size, labor markets, and the age structure of a country.

People immigrate for many reasons. Jobs, safety, family reunification, education, and freedom draw them to new places. War, persecution, poverty, and environmental disaster push them from old ones. Most migration happens between neighboring countries, not across oceans. In 2020, the United Nations estimated that about 281 million people lived outside their country of birth, roughly 3.6 percent of the world's population. Immigration is often controversial. Host countries debate how many people to admit, how to integrate them, and what obligations they owe to newcomers. Economists generally find that immigration boosts growth, though the benefits are not always evenly shared.

Common categories

• Economic migrants: seeking work and opportunity.
• Refugees: fleeing war or persecution.
• Family reunification: joining relatives already settled.
• Students and skilled workers: temporary or permanent.

Immigration is not a new phenomenon. Humans have always moved. What has changed is the scale, the speed, and the role of borders in regulating who can cross.