World Migration: Causes and Consequences of Migration

• Migration is a permanent or semi-permanent change of usual residence across a defined boundary. It moves people into a new social and economic environment, which separates it from short-term mobility such as commuting or circulation.
• It works at every scale: within a district, between regions, and across international borders. Internal migration is far larger than international migration, especially in India and China.
  • The UNDP’s Human Development Report 2009 estimated about 740 million internal migrants worldwide, more than double the international stock.
• In 2024 there were about 304 million international migrants, 3.7% of the world’s population (UN DESA, International Migrant Stock 2024). At the end of 2025, 117.8 million people were forcibly displaced (UNHCR, Global Trends 2025).

Concept and Types of Migration

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Basic Terms

• Emigrant and immigrant describe the same person from the country left and the country entered. Out-migrant and in-migrant are the internal equivalents.
• Net migration = in-migrants − out-migrants. A positive balance adds to population (USA, Gulf states, Germany); a negative one subtracts (Pakistan, Bangladesh, India, Nepal).
• Migrant stock is the number of migrants living in a place at one time. Migrant flow is the number moving in a period.
• Historically, geographers recognised invasion, conquest, colonisation and immigration as the four broad forms. Modern migration is mostly economic and individual, regulated by states.

Classification

• Micro-scale moves (within buildings or campuses) and commuting matter for urban geography but are not migration in the demographic sense. Commuting creates daily urban rhythms and defines functional urban regions.
• Local moves within a city follow housing needs and the life cycle: marriage, children, retirement, suburbanisation.
• Seasonal migration follows climate and the farm calendar, as in transhumance, harvest labour and tourism work.
• William Petersen (1958) classified migration by the force behind it:
  • Primitive: driven by ecological pressure, as among nomads.
  • Forced (no choice) and impelled (some choice left): slave trade, refugee flight.
  • Free: individual choice of pioneers.
  • Mass: free migration that becomes a social movement, like the 19th-century European exodus.
• Categories increasingly blur: a drought-hit farmer who leaves for city work is both an environmental and an economic migrant. Temporary and circular moves are rising everywhere.

Forced Migration

• Forced migration arises from conflict, persecution, disasters or development projects (dams, mines, corridors).
  • Development-induced displacement is large but less visible: China’s Three Gorges Dam relocated about 1.3 million people, and India’s big dams, mines and industrial corridors have displaced millions, many of them tribal.
• Refugee: a person outside their country who cannot return owing to a well-founded fear of persecution for reasons of race, religion, nationality, social group or political opinion (1951 Refugee Convention and its 1967 Protocol).
• Asylum seeker: a person whose claim to refugee status has not yet been decided.
• Internally displaced person (IDP): displaced but still inside their own country, without the legal protection given to refugees.
• Climate or environmental migrant: forced or induced to move by sudden disasters or slow environmental change. There is no legal refugee status for such people.
• UNHCR Global Trends 2025 (data to end-2025):
  • 117.8 million forcibly displaced, the first fall in a decade (from 123.2 million at end-2024), mainly because of returns to Afghanistan, Syria and Sudan.
  • 41.6 million refugees (including 6 million Palestine refugees under UNRWA), 9 million asylum seekers and 68.7 million IDPs.
  • Sudan has the largest internal displacement, with 9.1 million IDPs.
  • About one in 70 people on Earth is forcibly displaced.

World Migration: Historical and Current Patterns

Historical International Migration (Before 1945)

• Pre-1945 migration consisted of large, long-distance transfers tied to colonialism, trade and labour demand. It left lasting marks on ethnicity, language and economy.
• European settler migration (16th–20th centuries):
  • Europeans moved to North America, Latin America, Australia, New Zealand and southern Africa, opened up by Columbus, Vasco da Gama and later colonial expansion. Over 50 million Europeans emigrated overseas between 1815 and 1930.
  • Consequences:
    • European-origin populations came to dominate North America and Oceania.
    • Christianity, European languages, science and institutions spread.
    • Settler economies (USA, Canada, Australia) were built on transferred capital, skills and institutions.
    • Indigenous populations collapsed through disease, conflict and dispossession, as with the Aztecs and the Incas.
    • Mixed populations emerged, such as the mestizos of Latin America.
• The Atlantic slave trade (16th–19th centuries):
  • The largest forced migration in history before the 20th century. About 12.5 million Africans were embarked, mainly from West and West-Central Africa, for plantations in Brazil, the Caribbean and North America.
  • It followed the triangular trade: manufactured goods from Europe to West Africa, enslaved people to the Americas, and sugar, cotton and tobacco back to Europe.
  • Consequences:
    • The African diaspora of the Americas formed (Brazil, the Caribbean, the USA).
    • Racial hierarchies became entrenched.
    • Mixed groups emerged: mulattoes (European and African) and zambos (African and Indigenous).
• Industrial and plantation labour:
  • The Industrial Revolution drew workers from southern and eastern Europe and Ireland to industrial cores, and then across the Atlantic.
  • After slavery was abolished (Britain, 1833–34), the indenture system shipped over a million Indians and many Chinese under contract to plantations:
    • sugar in Mauritius, Fiji, Guyana, Trinidad, Suriname and Natal;
    • tea in Sri Lanka, rubber in Malaya;
    • cloves in Zanzibar.
  • These moves created the Indian and Chinese diasporas of the tropics.

Modern Migration (After 1945)

• Modern migration is more selective, more temporary, more global and more regulated than the colonial mass movements. In Wilbur Zelinsky’s (1971) terms, it belongs to high-mobility societies with diverse streams.
  • Selective: specific groups (skilled professionals, contract workers, students, refugees) move, not whole populations.
  • Temporary: many are sojourners on fixed contracts, as in the Gulf.
  • Global: cheaper transport has reduced the friction of distance, so flows link every continent.
  • Regulated: visas, quotas, points systems and sponsorship rules now decide who may move.
• Phase I, 1945–1960: political restructuring:
  • Partition of India (1947): about 14–15 million people crossed the new borders. India’s 1951 Census counted 7.3 million displaced persons.
  • Israel (1948): Jewish immigration and the displacement of Palestinians into Jordan, Lebanon and Syria.
  • Decolonisation: return of European settlers from Asia and Africa.
  • Europe’s reconstruction: labour shortages drew Algerians to France and Turks and Yugoslavs to Germany and Switzerland, the base of today’s multicultural Europe.
• Phase II, 1960s–1980s: labour migration:
  • The oil boom after 1973 turned the Gulf into a major destination for South and South-East Asian contract workers, who rarely settle permanently.
  • Skilled migration to the USA, Canada, Australia and the UK grew after their immigration laws were reformed in the 1960s: first doctors and engineers, then IT professionals and academics from the 1990s. This raised fears of brain drain.
• Phase III, since about 1990: globalisation and crisis:
  • South–North flows driven by income gaps; East–West flows after the break-up of the USSR and EU enlargement.
  • Waves of conflict displacement:
    • Afghanistan, Iraq, Rwanda (1994), Sudan and South Sudan;
    • Syria since 2011, Venezuela since 2015, Ukraine since 2022, Sudan since 2023;
    • the Rohingya flight from Myanmar to Cox’s Bazar in Bangladesh (2017).
  • Intra-African distress migration linked to drought, food insecurity and conflict in the Sahel and the Horn of Africa.
  • The 2015 European refugee crisis, when over a million people, most of them Syrians, Afghans and Iraqis, crossed the Mediterranean and the Balkans into Europe.

Refugee Geography

• Africa is a core region of displacement, where environmental stress and political instability reinforce each other:
  • The Sahel: chronic drought, desertification and recurrent food crises push people towards wetter, resource-richer neighbours and coastal cities. Armed conflict in Mali, Burkina Faso and Niger has added to the flight.
  • The Great Lakes: the Rwandan genocide (1994) sent over a million people into eastern Zaire (now the DR Congo) and Tanzania. Conflicts in Burundi and the DR Congo keep refugee corridors into Uganda, Tanzania and Kenya active.
  • New states and civil wars: South Sudan, independent in 2011, fell into civil war in 2013; its refugees went to Uganda, Ethiopia and Sudan. The Sudan war since April 2023 produced the world’s largest displacement crisis.
• West Asia: Palestinian displacement since 1948; the Iraq wars; the Syrian war since 2011, which made Türkiye the largest refugee host for years; Yemen’s conflict.
• South and South-East Asia: Afghans in Iran and Pakistan over four decades; Rohingya in Bangladesh; Tibetans, Sri Lankan Tamils and Chakmas in India.
• Patterns:
  • Most refugees stay in neighbouring, low- and middle-income countries. In 2024 Iran hosted the most refugees, followed by Türkiye, Germany, Uganda and Pakistan.
  • About seven in ten refugees come from just six countries, and most live in protracted displacement of five years or more.
  • The environment–conflict nexus (drought → competition over land and water → conflict → displacement) and weak states on the periphery generate most outflows.
  • These flows are push-dominated; pull factors matter only in the choice among nearby safe places.

Current Stock and Corridors

• Size: 304 million international migrants in 2024, nearly double the 154 million of 1990, yet still only 3.7% of humanity. About 48% are women and girls.
• Destination regions:
  • Europe hosts the most (94 million), then Northern America (61 million) and Northern Africa and Western Asia (54 million).
  • In Central and Southern Asia and in Eastern and South-Eastern Asia, migrants are under 1% of the population.
• Top destination countries:
  • USA (52.4 million), Germany (16.8 million), Saudi Arabia (13.7 million), the UK (11.8 million), France (9.2 million).
  • Migrants form 77% of Qatar’s and 74% of the UAE’s population.
• Top countries of origin:
  • India (18.5 million), China (11.7 million), Mexico (11.6 million), Ukraine (9.8 million), Russia (9.1 million).
• Main corridors:
  • Mexico–USA (about 11 million), the largest. Others include Afghanistan–Iran, Syria–Türkiye, Russia–Ukraine and India–UAE (IOM, World Migration Report 2026).
  • Between regions: Latin America to Northern America (27 million) and Central and Southern Asia to Northern Africa and Western Asia (20 million).
• Regional character:
  • Nearly 45% of migrants live within their region of origin. The share is 74% for Europeans and 64% for migrants from sub-Saharan Africa.
  • Central and Southern Asia sends 75% of its emigrants outside the region, mainly to the Gulf, Europe and North America.
• Labour: about 168 million international migrant workers (2022), two-thirds of them in high-income countries.

Remittances

• Remittances reached about US$ 905 billion in 2024, of which US$ 685 billion went to low- and middle-income countries (IOM, World Migration Report 2026). They now exceed official development assistance and foreign direct investment combined for these countries.
• Top recipients in 2024: India (US$ 137.7 billion), Mexico (US$ 67.9 billion), the Philippines, France and Pakistan (World Bank).
• Dependence is highest in small or landlocked economies: remittances equal 47% of GDP in Tajikistan, 39% in Tonga and about 26% in Nepal and Nicaragua.
• Effects of remittances:
  • They are counter-cyclical: they often rise when the home country faces a disaster or recession, because migrants send more.
  • They reduce poverty and finance schooling, health and housing, but much is spent on consumption and land, with limited productive investment.
  • Heavy dependence can create a “remittance economy” with high imports, rising land prices and a weaker incentive to build local industry.
• India’s place: India is the largest source of international migrants (18.5 million) and the largest receiver of remittances; it also hosts about 4.8 million immigrants, mostly from Bangladesh, Nepal and Pakistan.
• Sending money remains costly. The average cost of sending US$ 200 to sub-Saharan Africa was nearly 8% in 2023, against the SDG target of 3%.

Diaspora and Transnationalism

• A diaspora is a population living outside its homeland that keeps a shared identity and links with it: the Jewish, Armenian, Chinese and Indian diasporas.
• Transnationalism is the process by which migrants build and sustain social, economic and political fields across borders. They live “here and there” at once.
• Why transnational ties have multiplied:
  • Cheap air travel, smartphones, video calls and social media keep daily contact alive.
  • Digital remittances and cross-border payment links, such as India’s UPI links with Singapore and the UAE, cut costs.
  • Dual citizenship and diaspora schemes, such as India’s Overseas Citizen of India card and the Pravasi Bharatiya Divas held since 2003.
  • Diaspora investment, philanthropy and lobbying: Indian-origin leaders in the USA, UK and Canada; Silicon Valley–Bengaluru links.
  • Temporary and circular visa regimes keep migrants tied to home.
  • Identity politics and homeland causes (Khalistan, Tamil Eelam, Kurdish movements) keep political ties alive, sometimes contentiously.
• Recent diasporas formed by push–pull balances:
  • Ukrainians (war, from 2022) across Europe.
  • Venezuelans (economic collapse and repression) across Latin America.
  • Syrians and Afghans (war) in Türkiye, Iran, Pakistan and Germany.
  • Rohingya (persecution) in Bangladesh.
  • The fast-growing Indian student and professional diaspora in Canada, the USA, the UK and Australia, pulled by education, jobs and permanent-residence pathways.

Causes of Migration

• Migration is multi-causal and selective. Everett S. Lee (1966) explained it as the balance of push factors at the origin and pull factors at the destination, filtered by intervening obstacles and personal factors, one of several theories of migration.

Economic Causes

• The dominant driver of modern migration.
• Push: unemployment, underemployment, poverty, low farm productivity, small and fragmented holdings.
• Pull: higher wages, regular jobs, diversified economies.
• Rural–urban migration within developing countries; South Asia to the Gulf; skilled migration to OECD countries.
• Neoclassical theory reads this as a response to wage differentials; household theories read it as risk diversification.

Social and Demographic Causes

• Education and health care, better amenities and marriage. Marriage is the main cause of female migration in South Asia.
• Family reunification and chain migration through kin networks.
• Lifestyle and amenity moves: retirement migration to the Sun Belt or the Mediterranean, and counter-urbanisation.
• Demographic imbalance:
  • Origins with young, fast-growing labour forces (sub-Saharan Africa, South Asia).
  • Destinations with ageing, shrinking ones (Europe, Japan, the Gulf’s small native workforces).

Political Causes

• War, civil conflict, ethnic violence, persecution and state collapse produce refugees, asylum seekers and IDPs.
  • West Asia: Syria, Iraq, Yemen, Afghanistan.
  • Africa: Sudan, South Sudan, the Democratic Republic of the Congo, the Sahel.
  • Europe: Ukraine.
• State policies also cause or channel moves:
  • immigration quotas and points systems;
  • population transfers;
  • partition of territories (India 1947, Cyprus 1974);
  • expulsions, such as Asians from Uganda in 1972.
• These flows are mainly push-driven: survival, not opportunity, is the motive.

Environmental Causes

• Sudden-onset events: floods, cyclones, earthquakes. In 2024, disasters caused 45.8 million new internal displacements, more than conflict (20.1 million).
• Slow-onset change: desertification and drought in the Sahel, salinity and sea-level rise in the Ganga–Brahmaputra delta and small island states, glacier retreat.
• The World Bank’s Groundswell report (2021) projected that, without strong action, climate change could force up to 216 million people to move within their countries by 2050, mostly in sub-Saharan Africa, South Asia and East Asia.
• Climate migrants:
  • Usually move internally or to neighbouring countries. Their decisions mix climate stress with economic and political factors.
  • Policies for resettlement:
    • planned relocation with land and livelihoods (Fiji’s relocation guidelines);
    • migration with dignity and labour-mobility pathways (Kiribati);
    • the Falepili Union treaty (2023) offering residence in Australia to Tuvalu citizens;
    • disaster-risk reduction, insurance and climate-resilient livelihoods so that people can choose to stay.

Perception and Choice

• Push and pull are perceived, not objective. The same village repels young people seeking jobs and attracts retirees seeking quiet; the same city is a magnet to one family and a threat to another.
• Julian Wolpert’s (1965) idea of place utility explains this: people compare their present place with the alternatives they know about, within a limited action space, and move once dissatisfaction crosses a threshold.
• Networks shape perception. Successful earlier migrants send back money and stories, and destinations known through kin attract far more than equally good but unknown places.

Population Pressure and Migration Prospects

• Areas of population pressure (South Asia, the Sahel, Central America) generate the strongest wish to emigrate. Migration prospects, however, depend on destination policies, networks and the ability to pay.
• The open frontiers of the 19th century (the Americas, Australia) absorbed Europe’s surplus. Today’s pressure areas face closed borders, selective visas and irregular routes: the Mediterranean, the Darién Gap, the Bay of Bengal.
• Hence the poorest rarely emigrate far. Most pressure is absorbed by internal and regional migration.

Consequences of Migration

• Migration is both a response to spatial inequality and a cause of further change. Its effects differ between origin and destination and between kinds of migrant.

Economic Consequences

• Positive:
  • Remittances pay for food, health, schooling, debt repayment, housing and farm inputs.
  • They stabilise the balance of payments: they financed around half of India’s merchandise trade deficit in recent years.
  • Labour-deficit regions gain workers. The Green Revolution in Punjab, Haryana and western Uttar Pradesh relied on migrant labour from eastern Uttar Pradesh, Bihar, Madhya Pradesh and Odisha.
  • Return migrants bring savings and skills; diasporas bring investment, trade links and technology (brain circulation).
• Negative:
  • Brain drain of doctors, nurses and engineers.
  • Exploitation of low-skilled migrants: wage theft, debt bondage and, in the Gulf, the kafala sponsorship system.
  • Growth of the informal sector and pressure on urban economies.
• Labour governance in the Gulf has begun to change. Qatar removed exit permits and the employer’s no-objection requirement for changing jobs and introduced a minimum wage in 2020; Saudi Arabia’s 2021 labour reforms eased job mobility. Enforcement remains uneven.

Brain Drain, Brain Gain and Brain Circulation

• Brain drain: the loss of educated and skilled people to richer countries. It hurts most where skills are scarce, as with doctors and nurses leaving sub-Saharan Africa, the Philippines and parts of India.
• Brain gain: the prospect of emigration encourages more people to acquire skills, and not all of them leave; remittances and returnees also add to skills at home.
• Brain circulation: professionals move back and forth, carrying knowledge, capital and networks. The Silicon Valley–Bengaluru–Hyderabad links and the return of Taiwanese and Chinese engineers who founded firms at home are examples.
• Ethical recruitment codes, such as the WHO Global Code of Practice on the International Recruitment of Health Personnel (2010), try to limit the drain from the most fragile health systems.

Demographic Consequences

• Migration redistributes population and speeds urbanisation.
• Selectivity distorts both ends:
  • Origins lose young men. The hill districts of Uttarakhand and parts of Bihar have more women, children and elderly.
  • Destinations gain working-age men. Delhi, Surat and the Gulf states have very low sex ratios.
• In developed countries, migration now drives population change more than fertility does. It slows ageing but cannot reverse it.
• Urban demography:
  • In-migration adds to city growth directly, and indirectly through the births to young migrant couples.
  • It inflates the working-age share and the share of single men.
  • It concentrates particular ethnic, caste and language groups in particular neighbourhoods.

Social and Cultural Consequences

• Positive:
  • Diffusion of ideas, technology and new norms, including smaller families, girls’ schooling and health awareness.
  • Cultural diversity and cosmopolitanism; weaker caste and community rigidity.
• Negative:
  • Loosening of traditional family and community bonds.
  • Anonymity and alienation in cities.
  • Ethnic tension and nativism, from “sons of the soil” movements in India to anti-immigrant politics in Europe and the USA.
  • Crime, drug abuse and marginalisation where migrants are excluded.

Spatial and Settlement Consequences

• Push–pull flows create new settlement forms:
  • Ethnic enclaves: Chinatowns, Little Indias, Southall in London.
  • Refugee camps that become towns: Dadaab in Kenya; Kutupalong at Cox’s Bazar, the world’s largest refugee camp.
  • Labour camps and migrant dormitories in the Gulf.
  • Expatriate compounds and gated estates.
  • Slums and squatter settlements on urban fringes and floodplains.
  • Remittance landscapes of new houses in Kerala, Punjab and the Philippines.

Environmental Consequences

• Negative:
  • Unplanned urban expansion, slums, water shortage, air and water pollution, solid-waste crises and a larger urban ecological footprint.
  • At the origin, abandoned terraces and fields can degrade.
• Positive: depopulated uplands sometimes see forest regrowth, and remittances can finance cleaner fuels and better housing.

Gender Consequences

• Male out-migration:
  • Women left behind carry farm and household work and head households: the feminisation of agriculture.
  • They gain decision-making power but also face isolation and insecurity.
• Female migration:
  • Nursing, domestic and care work bring independence and income.
  • It also brings vulnerability: trafficking, abuse and insecure contracts.

Geographical Synthesis

• Migration expresses core–periphery relations: labour flows from the periphery (rural areas, poorer countries) to the core, and remittances, goods and ideas flow back.
• It is both a cause and a consequence of development. Uneven development starts flows; flows then reshape both regions, sometimes narrowing gaps through remittances and sometimes widening them through the loss of skills.
• Its effects work through feedback loops: each wave of migrants builds networks and expectations that sustain the next wave, so streams persist long after their first causes fade.

Rural–Urban Migration Trends

• Developed countries went through intense rural–urban migration during the Industrial Revolution (about 1750–1950). Most now show counter-urbanisation, as congestion, pollution and costs push people to suburbs and small towns. Global cities (New York, Tokyo, London) still attract migrants because of their command functions.
• Developing countries (South Asia, sub-Saharan Africa, parts of Latin America) still have dominant rural–urban flows, directed to capitals, metropolitan regions and growth centres.
  • Push: rapid rural population growth, fragmented holdings, falling farm returns, disguised unemployment, poor services, agrarian distress.
  • Pull: jobs in industry, services and the informal sector; schools and hospitals; social mobility.
• Consequences in cities: overcrowding and strain on transport, water, drainage and power; slums, squatter settlements and pavement dwellers; a swelling informal sector; urban poverty; pollution and waste; social exclusion and crime where integration fails. Migrant children and adolescents in informal settlements face poor sanitation and interrupted schooling.
• Consequences in villages: loss of young workers; feminisation of agriculture; dependence on remittances; ageing; sometimes the consolidation or abandonment of farmland.
• In much of the developing world, push exceeds pull. Cities grow faster than formal jobs, giving rise to over-urbanisation, slums and the transfer of rural poverty to the city. W. Arthur Lewis’s labour transfer runs into the informal sector rather than into factories.
• Responses:
  • Rural development and providing urban amenities in rural areas (PURA, the Shyama Prasad Mukherji Rurban Mission).
  • Satellite towns, counter-magnets and growth centres; regional planning.
  • Slum upgrading, low-cost rental housing and inclusive services.
  • China’s easing of the hukou household-registration system and its promotion of small and medium towns.

Global Governance

• Global Compact for Safe, Orderly and Regular Migration (2018): non-binding, 23 objectives.
• Global Compact on Refugees (2018): burden- and responsibility-sharing.
• SDG targets 10.7 (well-managed migration policies) and 10.c (remittance costs below 3%).
• Bilateral labour mobility agreements, such as India’s with Japan, Germany, Israel and Taiwan, and regional free-movement zones (EU, ECOWAS).