People, as they have always done, move from country to country, or internally within a country, leaving one location to settle or work in another^[1]. Overall, in 2020, about 3.6 percent of the world’s population lived in a country other than the one they were born in, up somewhat from the 2.8% in 1995^[2]. While not a large percentage globally, that still amounts to 281 million people in 2020, roughly the population of Indonesia, the 4th most populous country in the world. This number includes emigrants, who are people that have moved permanently to another country (80 million in 2019), overseas workers, who work for a period of time in another country and then return home (169 million)^[3], and refugees who flee wars and natural disasters (32 million). 

With the exception of refugees, most migrants live and work outside their native country for economic reasons and greater opportunities. Not surprisingly, two thirds of migrants settle in high income countries, with over 60% of migrant workers located in western Europe, North America, and the oil rich Arab States.

The United States hosts the largest number of migrants in the world, about 46.6 million in 2015, or about 14.5% of the population, but a number of wealthy countries, such as Canada, Australia, and Germany host more migrants as a percentage of their populations. Much of what applies to the economics of migration in the United States applies to immigration to wealthy countries in general, for that reason we will look at US immigration in detail before taking a more general look at world migration.

A note on terminology. An immigrant is a person who has moved permanently to another country from their country of birth. They are emigrants from their country of birth. The term overseas worker is used when referring to migrants from sending countries, while we will use the term guest worker when speaking about these same migrants from the point of view of the receiving country. International migrants include anyone who currently resides outside the country of their birth, which includes immigrants, overseas workers, and refugees. In the US, there are far more immigrants than guest workers, but that is not true everywhere: the oil rich Arab countries allow only guest workers, for example.

^[1] In the US each year about 14% of the population moves which is about equal to the entire accumulated immigrant population. We will not be looking at internal migrations, although it is an interesting subject and lends insight to the benefits of migration between countries.

^[2] https://worldmigrationreport.iom.int/wmr-2022-interactive/ accessed Mar 3, 2023

^[3] Many of these “overseas workers” may become permanent residents in countries that allow for such as status.