The global population ballooned by about 1.7 billion people between 2000 and 2020. But growth was uneven around the world and, in some places, immigration played a key role.
In 14 countries and territories, in fact, immigration accounted for more than 100% of population growth during this period, meaning that populations there would have declined if not for the arrival of new immigrants.
In 17 other countries, populations did decline between 2000 and 2020. But the decreases were smaller than they otherwise would have been due to growth in these countries’ immigrant populations.
This Pew Research Center analysis examines the places globally where immigration accounted for all population growth between 2000 and 2020, or where immigration helped avoid larger population losses.
The analysis is based on changes in overall country populations and their foreign-born (immigrant) populations. Overall population change is calculated based on 2000 and 2020 population estimates in the 2022 update to the United Nations’ World Population Prospects. Total fertility rates and median ages as of 2020 also come from this publication.
Changes in immigrant populations come from the UN’s 2022 migrant stock estimates for 2000 and 2020. We subtract immigrant population change from overall population change to show how overall populations would have changed without changes in immigrant populations. Migrant stocks, as opposed to migrant flows, measure the total foreign-born population in a country, rather than only recent arrivals. The differences between migrants from 2000 to 2020 are therefore due not only to new immigration, but also due to deaths and departures of earlier immigrants.
The places where populations grew only through immigration between 2000 and 2020 – and those where population losses were mitigated by immigration – are geographically scattered. What they tend to have in common is low fertility rates and aging populations. The only way a country’s population can increase, aside from having more births than deaths, is through immigration.
Population decline can be a challenge for countries experiencing it. When deaths and emigration outnumber births and immigration, countries are left with aging populations and dwindling numbers of working-age people to fill out the labor force and support older adults.
Where immigration staved off population losses
The places where immigration accounted for all population growth between 2000 and 2020 range from large countries in Europe to small island nations in the South Pacific.
Germany’s population grew by 1.7 million people between 2000 and 2020. But it would have shrunk by more than 5 million people without the arrival of new immigrants. During these years, many new immigrants arrived in Germany from Poland, Syria, Kazakhstan and Romania. Women in Germany have 1.5 children on average – far below the fertility rate of about 2.1 children per woman needed for each generation to replace itself – and half of people in Germany are older than 45.
Italy’s population grew by 2.7 million people between 2000 and 2020. However, if not for immigration from places like Romania, Ukraine and Albania, Italy’s population would have declined by 1.6 million people. Italy’s fertility rate is only 1.3 children per woman and its median age is 46.
In the Czech Republic, the overall population grew by 300,000 in 20 years, but immigrants again accounted for all growth. Without new immigrants – many of whom came from other European countries – the Czech population would have shrunk by more than 20,000. As of 2020, women in the Czech Republic had an average of 1.7 children, while the country’s median age was 42.
Portugal’s population grew modestly between 2000 and 2020 – by fewer than 40,000 people – but it would have shrunk by more than 310,000 people without new immigrant arrivals. Many migrants to Portugal were born in Angola, Brazil or France. Portugal’s fertility rate is 1.4 and its median age is 45.
Apart from Europe, immigration also played an important role in avoiding population losses elsewhere in the world.
The population of the United Arab Emirates grew by 6.1 million people between 2000 and 2020 but would have declined by 210,000 without new immigrants. Many of the UAE’s new arrivals were from South Asian countries or Egypt. The average woman in the UAE has 1.5 children, while the country’s median age is 32.
Several smaller countries and territories were also spared population decline only through the arrival of new immigrants. Aruba, the Cook Islands, Curacao, Dominica, the Falkland Islands, Liechtenstein, Monaco, Sint Maarten and Tokelau were all in this category.
Where immigration mitigated population losses
In 17 other countries and territories, populations declined between 2000 and 2020 but would have dropped even more – in some cases much more – without growth in their immigrant populations.
In Japan, fertility rates have plummeted to an average of only 1.3 children per woman and the median age is now 48. More people are dying each year than are being born, and Japan’s population declined by over 1.1 million people between 2000 and 2020. However, Japan’s population would have fallen by twice as much (2.2 million people) during this period if not for the arrival of new immigrants. During these years, the foreign-born population of Japan grew from 1.7 million to 2.8 million. Many immigrants to Japan have come from China, South Korea, Vietnam and the Philippines.
Romania’s population shrank by about 2.5 million between 2000 and2020 but would have declined by more than 3 million if not for new immigrants, many of whom are from Moldova. Romania has a fertility rate of 1.7 and a median age of 42.
Greece’s population declined by about 500,000 people between 2000 and 2020. But it would have decreased by 700,000 if not for an increase in the country’s foreign-born population. Similarly, Hungary’s population shrank by 440,000 – but would have fallen by 730,000 without new immigrants. Both countries have low fertility rates and older populations.
In other countries where populations declined, immigrant populations did not increase between 2000 and 2020. This can happen when deaths and departures among earlier immigrants outnumber new immigrant arrivals.
Causes and consequences of population decline
Around the world, women are having fewer children. Women have increasingly put off or forgone childbearing as their average years of education increase, rates of workforce participation climb, and reliable family planning methods become more accessible.
Globally, the total fertility rate – the number of children born to an average woman – declined from 2.7 to 2.3 between 2000 and 2020, a sizable drop in only two decades. It takes an average of about 2.1 children per woman for each generation to replace itself. Naturally, populations age as birth rates dwindle. During these years, the world’s median age increased from 25 to 30.
While fertility is declining all over the world, the impact on population change is uneven. Women still have an average of more than six children in a few African countries, while the average woman in South Korea and Singapore now has less than one child. Median ages, meanwhile, range from 14 in Niger to older than 50 in Monaco and the Vatican.
