Because of low fertility and increased longevity, the populations of most developed countries are likely to become smaller and older by the year 2050. As the size of the working-age population shrinks relative to the size of the population aged 65 and older, these societies could suffer profound economic, social and political consequences. International migration could help stem both overall declines and declines in the size of working-age populations, but the volume of immigration needed to maintain current population sizes varies widely and in many cases would entail substantial increases over recent or expected levels. In Italy, for example, the number of immigrants would have to grow to roughly 20 times the expected levels to maintain the total population size and to about 30 times the projected level to maintain the size of the working-age population. These are among the key findings of a United Nations study on replacement migration.1

The study focused on eight countries and two regions whose fertility levels are below replacement level: France, Germany, Italy, Japan, the Republic of Korea, the Russian Federation, the United Kingdom, the United States, Europe and the European Union. In the late 1990s, the total fertility rate in these countries and regions ranged from 1.2 to 2.0 births per woman. Five countries (France, Germany, Italy, Korea and the United Kingdom) had populations of less than 100 million in 1995, two (Japan and Russia) had populations of about 125-150 million, and the United States had a population of about 270 million. Overall, Europe's population was around 725 million, and that of the European Union was about 375 million.

Annual flows of international migration have varied widely among these countries. While France, Germany, Japan and the United Kingdom received fewer than 100,000 immigrants in 1998, the United States received nearly 700,000. In 1990, immigrants accounted for 1-10% of these populations.

Using the medium variant of the biennial United Nations population projections, the analysts examined the levels of international migration needed to achieve three population objectives in the study areas: maintaining the overall population size, maintaining the size of the population of working age (15-64) and maintaining the ratio of the working-age population to the population aged 65 and older. This last measure, known as the potential support ratio, is a key area of concern because of its effect on pension and other social service systems. In 1950, the ratio ranged from 5.8 to 18.2 in the study areas, but it has fallen steadily ever since; in 1995, the range was 4.1-12.6.

Medium Variant Projections

According to the medium variant projections, total fertility rates in all 10 populations will rise slightly but will remain below replacement level through 2050. Most of these populations will begin to drop before then, and the declines within the next 50 years may be dramatic--28% in Italy, 17% in Japan and 14% in Europe overall. The exception is the United States, whose population will keep growing, because fertility is near replacement level and the number of arriving immigrants is expected to remain high (about 760,000 a year). If these conditions continue, the U.S. population in 2050 will exceed the 2000 total by about 70 million.

Under the medium variant scenario, potential support ratios will change substantially (Table 1). In many countries, the ratio will fall by roughly half, but in Korea, it will tumble by about 80%, from 12.6 to 2.4. Italy, Japan and the European Union are projected to have ratios below 2.0; Italy's may approach 1.5.




Table 1. Projected potential support ratio and projected total number of immigrants under various scenarios, selected countries and regions, 1995-2050
Country or region 1995 Medium variant Medium variant with no migration Maintain total population Maintain working-age population Maintain ratio
France 4.36 2.26 2.26 2.33 2.49 4.36
Germany 4.41 2.05 1.75 2.26 2.44 4.41
Italy 4.08 1.52 1.52 2.03 2.25 4.08
Japan 4.77 1.71 1.71 2.07 2.19 4.77
Republic of Korea 12.62 2.40 2.40 2.49 2.76 12.62
Russian Federation 5.62 2.43 2.44 2.86 3.12 5.62
United Kingdom 4.09 2.37 2.36 2.49 2.64 4.09
United States 5.21 2.82 2.57 2.63 2.74 5.21
Europe 4.81 2.11 2.04 2.38 2.62 4.81
European Union 4.31 1.97 1.89 2.21 2.42 4.31
No. of Migrants (in 000s)
France na 525 0 1,473 5,459 93,794
Germany na 11,400 0 17,838 25,209 188,497
Italy na 660 0 12,944 19,610 119,684
Japan na 0 0 17,141 33,487 553,495
Republic of Korea na -450 0 1,509 6,426 5,148,928
Russian Federation na 7,417 0 27,952 37,756 257,110
United Kingdom na 1,200 0 2,634 6,247 59,775
United States na 41,800 0 6,384 17,967 592,757
Europe na 23,530 0 100,137 161,346 1,386,151
European Union na 16,361 0 47,456 79,605 700,506
Notes: The potential support ratio is the ratio of the population aged 15-64 to the population aged 65 and older. The second and third columns refer to the medium variant of the biennial United Nations population projections; the last three columns indicate the estimated numbers of international migrants required to achieve the given objective. na=not applicable.

France, Italy and the United Kingdom will receive an average of about 10,000- 20,000 immigrants a year, or between about 500,000 and one million in all, under this scenario. Japan will register no net migration, and Korea will experience a net loss. The remaining countries and regions (other than the United States) will gain roughly 135,000-428,000 immigrants annually, for totals of 7-24 million.

Effect of No Migration

In an alternative scenario, under which no international migration occurred after 1995, population declines would be generally similar to those in the medium variant projections. However, the U.S. population, without the expected high levels of immigration, would begin to decline after 2025. As a result, although the U.S. population would experience net growth for the period, the gain would be considerably smaller than the increase expected under the medium variant projection--only 16 million. France and Korea would register small population increases, because immigration under the medium variant was not substantial and its absence would therefore have little effect.

Without migration, the working-age population in every country and region in the study would fall faster than the total population. For example, in the European Union, the population aged 15-64 would decline by 30% between 2000 and 2050, while the total population would decline by 17%. Men and women aged 65 and older would represent between one-quarter and one-third of these 10 populations by 2050, and the potential support ratio would range from 1.5 (in Italy) to 2.6 (in the United States).

Maintaining Current Levels

If no international migration occurred after 1995, these populations would reach their highest levels sometime between 1995 (Germany, Italy, Russia and Europe) and 2035 (Korea), but immigration could help maintain those levels. The number of immigrants that countries would have to receive through the year 2050 to avert population decline ranges from about 1.5 million in France and Korea to 17-28 million in Germany, Japan and Russia, and 100 million in Europe as a whole (Table 1). In the United States, the number of immigrants required to maintain the population size (6.4 million) is considerably smaller than the number projected in the medium variant (41.8 million), but in all of the other countries and regions studied, the volume of international migration would have to increase substantially. In Germany, it would have to grow by about half, and elsewhere it would need to roughly triple (France) or quadruple (Europe). Italy would have to receive about 20 times the number of immigrants expected to maintain its population size.

Under this scenario, the proportion of the population made up of people who had immigrated after 1995 or their descendants would range from 3% (in the United States) to 29% (in Italy) in 2050. Potential support ratios in 2050 would be slightly higher under this scenario than they would in the absence of international migration, but the range would remain narrow (2.0-2.9).

Similarly, if migration ceased after 1995, the working-age populations of these countries and regions would peak between 1995 (Germany, Italy, Japan and the European Union) and 2020 (Korea). The levels of immigration that would be required to maintain the size of this subgroup are far higher than those needed to hold the overall population constant: 5-6 million in France, Korea and the United Kingdom; nearly 20 million (or about 30 times the projected total) in Italy; roughly 35 million in Japan and Russia; and 161 million in Europe. By 2050, immigrants and their descendants would represent a sizable share of the total population of these countries; the proportion would range from 8% in the United States to 39% in Italy. Again, potential support ratios would increase very slightly.

Finally, the analysts projected the volume of immigration needed to keep potential support ratios at their 1995 levels. In all 10 countries and regions, the numbers are enormous: roughly 60 million in the United Kingdom; more than one-half billion in Japan, the United States and the European Union; and five billion in Korea. Under this scenario, the proportion of the population in 2050 who had immigrated after 1995 or were descendants of immigrants would range from 59% in the United Kingdom to 99% in Korea. The analysts observe that "maintaining potential support ratios at current levels through replacement migration alone seems out of reach, because of the extraordinarily large number of migrants that would be required."


The analysts point out that "the prospects of population decline and population ageing during the coming decades, and particularly the rapid and extensive reduction of the potential support ratio in many countries, raise a number of crucial issues in the areas of employment, economic growth, health care services, pensions and social support services." In view of the projected trends, they urge governments to undertake "objective, thorough and comprehensive reassessments" of labor-force participation; appropriate retirement ages; the nature and types of retirement and health care benefits available for aging citizens; policies and programs pertaining to international migration; and the integration of immigrants and their descendants into society.--D. Hollander


1. United Nations Population Division, Replacement Migration: Is It a Solution to Declining and Ageing Populations? New York: United Nations, 2000.