War and societal upheaval have been causing Afghans to leave their country for more than four decades, and its neighbour to the south-east has been most affected. Pakistan has about 1.4 million registered Afghan refugees, the third-highest refugee total in the world, but the actual number may be more than double this.
The UN estimates that there are 82m forcibly displaced people around the world from countries including Afghanistan, Syria, South Sudan and Myanmar. This is a fraction of the world’s total number of migrants – a figure that continues to grow.
Here we examine important trends in global migration.
How has the number of international migrants changed over the past half century?
The world is on the move: more people are migrating to other countries in search of safety or better economic prospects.
Experts, such as Dr Michael Clemens of the US-based Centre of Global Development, have written that in poorer countries, it tends to be wealthier citizens who leave and economic development in low-income countries leads to more emigration.
In 1970, there were 84m people living outside their country of birth, UN statistics show, but by the year 2000, that figure had jumped to 174m. In 2019, the number was 271m.
Even accounting for world population growth, mobility has increased. In 1970, 2.3 per cent of people lived outside their home country, a proportion that grew to 2.8 per cent by 2000 and 3.5 per cent by 2019.
Bill Ong Hing, professor of law and migration studies at the University of San Francisco and the author of numerous books about migration, including Defining America Through Immigration Policy, says several factors are at play and these vary across the world.
“It’s a combination of such things as political upheaval … there’s natural catastrophes like hurricanes and earthquakes and, related to that, there’s climate migration,” he says.
“We may not see a single incident, such as a hurricane, but it may be more gradual in terms of the fact that certain parts of the world are not as conducive as they were before to farming and agriculture.”
While some who move from one country to another are considered economic migrants, Prof Hing says many are fleeing poverty or climate-induced stresses.
Where do migrants come from?
About four in 10 of the world’s migrants come from Asia, the largest number for any continent. However, Asia has about 60 per cent of the global population, so its contribution to migration is actually disproportionately low.
Among nations, India accounts for the largest share of the world’s migrants, with a diaspora of about 18m, but this is perhaps a modest number given the country’s population of 1.37 billion.
Mexico, with less than a tenth of India’s population, accounts for about 12m migrants, with the Mexican-US corridor described as the busiest migration route in the world. But with a falling birth rate and a healthy economy, analysts have predicted this northward movement will slow.
China, the world’s most populous nation, is the third-biggest contributor to migration, with about 11m of citizens born within its borders now resident abroad.
However, for China, internal migration is much larger and has been described as the largest movement of people globally over the past century.
Estimates put the number of internal migrants in China at considerably more than 100m and as much as one third of the country’s labour force is accounted for by internal migrants.
Russia, where emigration and modest fertility rates have created concerns over population decline, is fourth.
The countries at numbers five (Syria) and 10 (Afghanistan) show how instability and war are important drivers of migration. A reported 6.7m Syrians are now refugees and in recent years the Syria-to-Turkey migration corridor has been the second-busiest in the world.
Where do migrants go?
Often called 'the land of opportunity', the United States has long exerted a magnetic pull on those in search of sanctuary, a better life and a share of the American dream.
It remains the nation with overwhelmingly the largest number of migrants as residents within its population, hosting about 51m (out of its 330m population), or almost one in five of the world's migrants, UN figures published in 2019 show.
Some nations have more migrants as a share of their population, including Germany, whose total of 13m is the world’s second largest.
About 1.8m are of refugee background, many from Syria, although this has sparked a backlash. Other western nations are potent draws, including the UK, whose 10m resident migrants place it fifth globally, the UN says. France, Canada, Australia and Italy occupy positions seven to 10.
Migration contributes to population growth in the UK and numerous other nations, but many countries of origin of the people involved have high birth rates, so are not experiencing population declines.
“Although migration in today’s world is having a significant impact on population size in regions of destination, its impact is much less significant in regions of origin,” a 2019 UN report said.
Employment opportunities in the Gulf states are significant in global migration, with Saudi Arabia hosting around the same number of migrants as Germany. The UAE is sixth globally.
Russia is fourth, with about 12m migrants, most from the Commonwealth of Independent States, the former Soviet Union. The country has almost as many of its own citizens living abroad, many in other CIS nations.
Contrary to some perceptions, most refugees remain in developing countries. Such nations reportedly hosted about 84 per cent of the 25.9m refugees in the world in 2018.
Are countries preventing or promoting migration?
Numerous developed nations, such as Germany, the UK and the US, have adopted high immigration rates as their birth rates declined to below-replacement levels. “Western Europe is going to follow the US in that regard,” says Prof Hing.
“There’s going to be resistance – I’m very well aware of the anti-immigrant populist movements … [but] it’s inevitable places like western Europe will become much more diverse.”
A 2019 UN report showed slightly more than one third of 111 nations analysed had policies to raise immigration, while about a quarter aimed to maintain levels. Only three had rules aimed at lowering immigration.
Certain wealthy nations that have not followed the high immigration model of the US, western Europe and Australasia are gradually allowing more people to arrive.
The Japanese population has been declining since 2011, but over the past three decades, the number of migrants in the country has tripled and now stands at about 3m from a population of about 126m.
Changes introduced in 2019 to allow more foreign workers to move to Japan are likely to result in further increases.
The arrival of refugees has sparked protests in East Asia, including in South Korea, where only a tiny fraction of refugee applications are granted.
While Prof Hing is “pleasantly surprised” that South Korea has accepted some Afghan citizens, he remains “sceptical of very progressive change in Asia”.
How will migration change over time and what geographical patterns will unfold?
The expectation is that as sub-Saharan Africa’s population grows fast it will become an increasing source of migrants.
One forecast indicates the region’s population will triple by 2100, by which time it will account for 35 per cent of the world’s population, compared to 13 per cent now.
Climate change is thought likely to become an increasing cause of migration, with one estimate suggesting it may have caused more than 1bn people to move by the middle of this century.
Prof Hing says figures of this magnitude are “very, very possible”, especially if robust action to address what is often described as the climate emergency is not taken. He also sees political instability as likely to continue to drive migration, partly because of a lack of international political will to deal with crises.
While sub-Saharan Africa’s population is forecast to continue to grow, the world population has been predicted to peak at around 2070. Even if that happens, Prof Hing expects migration to developed nations to continue.
“I do think that many countries will become reliant on migrants to sustain economic activity,” he says. “There will be some countries that are recruiting more than ever at that point.”
Sentiment on migration in the US and other parts of the world is “always cyclical” but he says that over the coming decades he expects “pro-immigrant sentiment will prevail in the US”.