Immigration is the fastest humane way for a low-fertility country to add young adults. A migrant arrives already raised and often ready to work, pay taxes, form a household, and have children. That speed makes immigration valuable. It also tempts governments to call a transfer of people a solution to fertility decline.
At the national level, migration can prevent population loss for decades. It can fill a hospital vacancy before a newborn could finish kindergarten. Because migrants are typically younger than the receiving population, they improve the age balance as well as the head count. Canada recently demonstrated how strongly immigration can separate population growth from native fertility: the country grew rapidly while its TFR fell to 1.25 in 2024.
The fiscal effect depends on who arrives and what happens afterward. A young worker with scarce skills may contribute more in taxes than she receives in services for many years. A child who migrates will first attend school, then work. Refugees often need costly help at arrival and may contribute more as language and employment improve. “Immigrants” are not one entry in a ledger.
Scale changes the answer. In its 2000 study of replacement migration, the United Nations calculated that keeping the European Union’s population from falling through 2050 would require average net migration of roughly 950,000 a year under its assumptions. Keeping the working-age population level required more. Holding the old-age support ratio at its 1995 level would have required hundreds of millions of migrants and descendants—an order of magnitude beyond an ordinary migration policy. Raising retirement ages was arithmetically far more plausible.
The figures are old projections, not a prescription for today. Their lesson has aged well. “Replacement” has several meanings. Enough migration to keep the total population stable may still leave the country older. Enough to keep the labor force stable may transform cities, schools, and politics faster than institutions can absorb. Enough to freeze the ratio of workers to retirees may be impossible.
Convergence within a lifetime
Migrants do bring fertility with them, especially when they arrive from societies where families are larger. The effect fades. Fertility usually moves toward the host-country pattern with years of residence and across generations, although the speed varies by origin, age at arrival, religion, education, and marriage pattern.
A 2025 European Bank for Reconstruction and Development analysis across nineteen European destinations found convergence within the first generation. Women from Asia, Europe, and Latin America approached local childbearing intensity after at least twelve years in the destination; convergence took longer for women from the Middle East, North Africa, and sub-Saharan Africa. Among second-generation women, the gap was much smaller: those with foreign-born mothers had only 8 percent more children ages zero to two in the household than comparable native-born women, against 76 percent more for recent immigrants from the higher-fertility regions.
That is not an assimilation failure. A migrant adapts because she now faces the same housing market, work schedule, courtship culture, and schools as her neighbors. Her daughter grows up inside them. If those institutions yield few children among the native-born, they will eventually yield few children among newcomers too.
The country left behind
Every working-age immigrant was a child someone else raised. When a rich country recruits a nurse from a poorer and younger country, it gains the years of care and education already invested in her. The origin country loses a daughter, a possible mother nearby, and a trained worker. Remittances return money. They do not staff the ward she left.
Migration can still be good for the migrant, her family, and both countries. Free people should generally be able to leave a place where their prospects are thin. Receiving countries gain energy and talent; origin countries gain remittances and networks. These gains deserve to be named because migrants are persons seeking lives, not demographic material to be allocated by a planner.
Competition will intensify as fertility falls in today’s origin countries. Latin America is already below replacement in much of the region. India is near it nationally. Even sub-Saharan Africa is declining. Five generations from now, there will be fewer youthful populations from which every aging country can recruit. At the global level there is nowhere else to recruit from.
A confident country can welcome immigrants and ask them to join its common life. It should do so with honest limits, enough housing, and institutions capable of integration. Immigration buys time and can enrich a nation. The time should be used to repair family formation, or the receiving country will merely extend its low-fertility settlement to the people it invited in.
Citations
- United Nations Population Division, Replacement Migration: Is It a Solution to Declining and Ageing Populations?, 2000.
- National Academies of Sciences, Engineering, and Medicine, The Economic and Fiscal Consequences of Immigration, 2017.
- European Bank for Reconstruction and Development, Transition Report 2025–26, “Fertility convergence among immigrants”, 2025.
- Hill Kulu and others, “Fertility by Birth Order among the Descendants of Immigrants in Selected European Countries”, Population and Development Review 43, no. 1, 2017.
- World Health Organization, WHO Global Code of Practice on the International Recruitment of Health Personnel, 2010.
- Statistics Canada, “Fertility and baby names, 2024”, 2025.