How did migration lead to the population of the world?

The developed regions as a whole will experience a

shrinking of population after 2040. According to the

medium-variant projection of the United Nations, the

world’s population is likely to increase from 7.6 billion in

2017 to 8.6 billion by 2030, the target year of the

Sustainable Development Goals, and to 9.8 billion in

2050.1 Most of this increase will take place in the

developing regions, while the developed regions will, for

the first time in recorded history, start to experience

negative population growth by around 2040 or 2050.

Under a scenario that assumes a net migration of zero,

the projected population of the developed regions would

be nine per cent smaller in 2050 than if current migration

trends continued. With no migration, or with equivalent

levels of immigration and emigration, the population of

the developing regions would be about one per cent

larger in 2050 than if current migration trends continued.

With fertility falling, the contribution of migration to

population change is likely to increase. Total fertility,

which stands at 2.5 births per woman at the world level

today, is projected to fall to 2.2 in 2050. Fertility in the

developed regions, which fell below the replacement

level of 2.1 births per woman shortly before 1980,

stands currently at 1.7 births per woman. Birth rates in

many developing countries, while declining, remain

relatively high. In the long run, the trend towards lower

fertility rates could result in an eventual stabilization of

the world’s population at around 11 billion people.

Migration already makes an important contribution

to population growth. Since the 1950s, the developed

regions continuously gained population due to positive

net migration. From 1950-1970 to 2000-2010, the level

of net migration to the developed regions increased

from 0.3 million to 3.1 million migrants per year.

However, the net inflow of migrants fell to about 2.2

million persons annually between 2010 and 2015.

Since the 1990s, migration has been the primary

source of population growth in the developed

regions. Migration is projected to be the only driver of

population growth in the developed regions starting after

2020. By 2050, it is expected that the population of the

developed regions will start to decline in size, as the net

inflow of migrants will no longer be sufficient to

compensate for the excess of deaths over births. The

impact of outmigration on population growth in the

developing regions is expected to remain minimal.

Indeed, for the next several decades, it is expected that

elevated levels of fertility in the developing regions will

continue to dwarf the role of net migration, which is

negative but relatively small (figure 1).

Migration and population change - drivers and impacts

Net migration refers to the difference between

numbers of immigrants and emigrants, who arrive in

or depart from a particular country or area in a given

time period, irrespective of country of birth or

citizenship. The “medium variant” of the United

Nations population projections assumes a

continuation of recent levels of net migration in future

years, whereas the “zero-net-migration scenario”

assumes that numbers of immigrants and emigrants

will be equal, starting in the period from 2015 to 2020.

Comparing these two scenarios provides useful

insights into the contribution of international

migration to population change

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