Immigration is one of the fastest humane ways for a low-fertility country to add young adults. A migrant may arrive ready to fill a hospital vacancy decades before a baby born today could, but she also arrives with a family, language, loyalties, losses, and plans of her own. Immigration can alter a country’s population and age structure quickly; it does not reverse low fertility globally or guarantee that migrants’ fertility will follow a single destination pattern.
At the national level, migration can prevent population loss for decades and improve the age balance because migrants are often younger than the receiving population. Canada recently showed how far population growth can separate from fertility: Statistics Canada reported a period total fertility rate (TFR)—not completed family size—of 1.25 in 2024 while the population continued to grow.
The fiscal effect depends on who arrives. A young worker with scarce skills may contribute more in taxes than she receives in services for many years, while a refugee who needs language instruction and help entering the labor market has a different path. Outcomes vary with age at arrival, education, earnings, family composition, eligibility, and the time horizon. Treating both as one demographic unit hides the people and the policy choices inside the average.
Scale eventually changes the answer. A United Nations exercise published in 2000 separated three goals that are still often confused: preventing total population decline, preventing decline in the working-age population, and preserving the existing ratio of people ages fifteen to sixty-four to people sixty-five and older. Each required a much larger migration path than the one before it. Under the report’s late-1990s assumptions, keeping the European Union’s population from falling through 2050 required average net migration of roughly 950,000 a year. Holding its 1995 support ratio required hundreds of millions of migrants and descendants.
Those figures are scenarios built from a late-1990s population projection, not a current forecast, quota, or policy recommendation. Migrants and descendants in the exercise are model inputs, not additional births for the world. Its durable lesson is about the denominator: migration can prevent population loss with flows far smaller than those required to freeze an age ratio while longevity rises. Retirement ages, health, participation, and productivity therefore remain part of any workable response; preserving a support ratio is not a neutral or necessarily realistic objective.
The host country changes fertility too
Migrant fertility often moves toward the destination-country pattern with time and across generations, but the pathway and endpoint vary. Origin, destination, generation, sex, parity, education, selection, partnership formation, and the measure used can all change the result. Some groups become native-like, some remain above native fertility, and some fall below it.
A 2025 European Bank for Reconstruction and Development analysis used harmonized labor-force surveys from nineteen European destinations between 2008 and 2023. It compared the presence of children ages zero to two among women of the same age and origin region—a child-presence or intensity proxy, not lifetime or completed fertility. The reported pattern moved toward the locally born pattern with time in the destination, but timing, selection, parity, sex, origin, destination, and the construction of the second-generation comparison limit any universal reading.
That measure is not lifetime fertility, and migration itself can rearrange when births occur. The pattern still bears on policy: migrants spend years inside the destination’s housing market, work schedule, schools, and expectations about family life. Exposure to that environment can matter, but it is not proof that all groups converge or that migration lowers global fertility.
That creates a limit that no immigration target can solve. If a country makes family formation unusually difficult for the native-born, newcomers may encounter some of the same constraints over time. Immigration can replenish a low-fertility country while also exposing another generation to its fertility conditions; it does not guarantee one endpoint or settle the global birth balance.
A person leaves, not just a worker
Every working-age immigrant was a child somewhere. When a rich country recruits a nurse from a poorer country, it receives years of care and education already invested in her; the origin country loses a trained worker and often a daughter who might otherwise have lived near aging parents. Remittances can improve the lives of the family she left. They cannot take her shift at the hospital.
None of this makes migration a wrong. A person should be able to leave a place where war, persecution, or poverty denies a decent life, and receiving countries can gain talent and energy from people who choose to join them. Governments also have obligations to maintain public order, sustain consent, and build the schools, homes, and institutions through which newcomers can enter a common life. Migrants retain claims to humane treatment, meaningful work, religious and civic freedom, and unity with their families. The balance begins by refusing to treat a person as imported labor with the inconvenient parts left behind.
Arrival into a common future New citizens taking the oath of allegiance at a National Park Service naturalization ceremony, September 2025. Immigration can add young adults quickly; it still requires enough trust to imagine a shared civic life. via Wikimedia Commons
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The demographic point is narrower: migration moves people across a border. It can replenish a nation, but it does not create an additional successor generation for the world.
That limit may become more binding as fertility falls in countries that now supply migrants. The timing and extent are projection-sensitive, and the cited evidence here does not establish a century-ahead supply path. Whether migration lowers global completed fertility relative to a no-migration path remains an unestimated counterfactual here.
A country can welcome immigrants and use the time they buy well. It can build homes, integrate newcomers, improve care, and ease the burdens that keep young adults from forming families. Immigration is valuable precisely because time is valuable. It is less convincing as an excuse to leave the underlying fertility problem untouched, and it is not a program of global renewal.
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.