Migration Theories and Patterns

Definitions and Classifications

Migration is the movement of people from one place to another with the intention of settling, permanently or temporarily, in the new location. Migration can be classified along several dimensions:

Dimension	Categories	Notes
Direction	Internal (within a country), international (crossing a national border)	Internal migration includes rural-urban, urban-urban, and rural-rural
Duration	Temporary (seasonal, circular), permanent	Circular migration involves repeated movement between origin and destination
Voluntariness	Voluntary (economic, social), forced (conflict, persecution, environmental disaster)	The distinction is often blurred in practice
Distance	Short-distance, long-distance, intercontinental	Ravenstein observed that most migration is over short distances
Legal status	Regular (documented), irregular (undocumented)	Irregular migrants lack legal authorisation to enter, stay, or work

Theoretical Frameworks

Ravenstein's Laws of Migration (1885)

Ernest Georg Ravenstein, based on an analysis of census data from the United Kingdom, formulated several "laws" of migration that remain influential:

1. The majority of migrants move only a short distance. Distance decay: the volume of migration decreases with increasing distance, because longer distances entail higher costs (financial, informational, psychological) and greater cultural adjustment.
2. Migration occurs in steps. Rural-urban migration often proceeds via intermediate towns rather than directly from village to large city (step migration).
3. Migration produces counter-currents. For every major migration stream, there is a smaller return flow.
4. Urban residents are less migratory than rural residents. Urban populations are already relatively mobile; rural populations have greater potential for long-distance movement.
5. Females are more migratory than males over short distances, but males dominate long-distance migration. This reflects historical gender roles: women moved locally for marriage; men moved further for employment.
6. Economic factors are the dominant cause of migration. People move primarily to improve their economic circumstances.
7. Most migrants are adults, not families. Young adults are most likely to migrate, as they have the longest period over which to reap the benefits.
8. Large towns grow more by migration than by natural increase.

Lee's Model of Migration (1966)

Everett Lee extended Ravenstein's work by developing a more formal model that identifies four elements in the migration decision:

1. Factors associated with the area of origin (push factors): conditions that encourage departure. These include economic factors (unemployment, low wages, poverty), social factors (discrimination, persecution, lack of services), environmental factors (drought, flooding, pollution), and demographic factors (population pressure).
2. Factors associated with the area of destination (pull factors): conditions that attract migrants. These include economic factors (higher wages, employment opportunities), social factors (political stability, freedom, education, healthcare), environmental factors (favourable climate), and demographic factors (family reunification, established diaspora).
3. Intervening obstacles: barriers between origin and destination that may prevent or discourage migration. Physical barriers include distance, mountains, oceans, and deserts. Political barriers include visa requirements, border controls, and immigration quotas. Economic barriers include the cost of travel and relocation. Psychological barriers include fear of the unknown, cultural adjustment, and separation from family.
4. Personal factors: individual characteristics (age, education, skills, risk tolerance, family ties) that mediate the migration decision. Two people facing identical push and pull factors may make different migration decisions due to differences in personal circumstances.

Lee's model recognises that the decision to migrate involves an assessment of the perceived costs and benefits of moving versus staying, filtered through individual characteristics and mediated by intervening obstacles. It also recognises that not all factors are positive or negative from the perspective of the individual: what is a push factor for one person (e.g., the closure of a local factory) may be neutral for another.

Structuralist Approaches

Structuralist theories of migration emphasise the role of structural economic forces, particularly the global capitalist system, in driving migration:

• Dual labour market theory (Piore, 1979): advanced economies have a dual labour market consisting of a primary sector (stable, high-wage, skilled employment) and a secondary sector (unstable, low-wage, unskilled employment). Native workers are reluctant to accept secondary-sector jobs, creating a structural demand for migrant labour.
• World systems theory (Wallerstein, 1974; Portes and Walton, 1981): migration is a consequence of the penetration of capitalist economic relations into peripheral regions through colonialism, trade, and investment. This penetration disrupts traditional livelihoods, displaces people from the land, and creates migration flows from periphery to core.
• New economics of labour migration (Stark and Bloom, 1985): migration is a household strategy to diversify income sources and manage risk, rather than an individual maximising earnings. Households send members to migrate as a form of insurance against local economic shocks (crop failure, unemployment).

Types of Migration

Internal Migration

Rural-urban migration is the dominant form of internal migration in developing countries. It is driven by the Harris-Todaro mechanism (expected urban wages exceed rural wages, even accounting for the probability of unemployment) and by the aspiration for modern lifestyles and services.

Urban-urban migration involves movement between cities, often from smaller to larger cities. In China, inter-provincial migration flows predominantly toward the coastal megacities (Shanghai, Shenzhen, Guangzhou, Beijing), reflecting the concentration of employment opportunities in the eastern seaboard.

Forced internal displacement results from conflict, environmental disasters, or development projects. As of 2023, approximately 62.5 million people were internally displaced worldwide, predominantly due to conflict (Syria, DRC, Afghanistan, Ethiopia) and disasters (Pakistan floods 2022, Philippines typhoons).

International Migration

Economic migration involves movement across national borders primarily for employment. Key corridors include South Asia to the Gulf States (approximately 35 million migrant workers from India, Pakistan, Bangladesh, Nepal, Philippines, and Sri Lanka work in Saudi Arabia, UAE, Qatar, Kuwait, Bahrain, and Oman); Eastern Europe to Western Europe; and Central America to the USA.

Forced migration includes refugees (people who have fled their country due to persecution, conflict, or violence and are protected under the 1951 Refugee Convention) and asylum seekers (people who have applied for refugee status but whose claims have not yet been determined). As of mid-2023, the UNHCR estimated 36.4 million refugees and 6.1 million asylum seekers globally.

Environmental migration is movement driven by environmental change or environmental disasters. The World Bank estimates that up to 216 million people could be internally displaced by climate change by 2050. However, establishing a causal link between environmental change and migration is complex, as environmental factors interact with economic, social, and political drivers.

Impacts of Migration

On the Country of Origin

Impact	Positive	Negative
Economic	Remittances (global remittances exceeded USD 650 billion in 2023, exceeding official development aid); return migrants bring skills and investment; reduced pressure on labour market	Brain drain (loss of skilled workers, particularly in healthcare and education); reduced tax base
Social	Exposure to new ideas and practices through return migrants and diaspora networks	Family disruption; dependency on remittances (Diaspora may reduce incentive for local economic activity)
Demographic	Reduced population pressure (particularly relevant for countries with high population growth)	Ageing population if working-age emigration exceeds natural increase

On the Country of Destination

Impact	Positive	Negative
Economic	Increased labour supply (particularly in sectors with shortages: healthcare, agriculture, construction, hospitality); entrepreneurial activity; increased demand for goods and services	Wage depression in low-skill sectors (contested; evidence is mixed); fiscal costs of integration and services
Social	Cultural diversity; culinary and artistic enrichment; demographic rejuvenation (in ageing societies)	Social tension; pressure on housing and public services; cultural conflict; political backlash (rise of anti-immigration parties)
Demographic	Mitigates population decline in countries with below-replacement fertility	Changes the ethnic and cultural composition of the population

Case Study: Mexico-USA Migration

Mexico-USA migration is one of the most studied international migration flows.

Scale and trends. In 2022, approximately 10.7 million Mexican-born residents lived in the USA, constituting the largest foreign-born population. Net migration from Mexico to the USA has declined since 2010, partly due to improved economic conditions in Mexico (GDP growth averaging 2--3% per year), tighter border enforcement (the USA has spent over USD 300 billion on border security since 2003), and demographic changes (Mexico's fertility decline has reduced the pool of potential migrants).

Remittances. Remittances from the USA to Mexico exceeded USD 60 billion in 2023, representing approximately 4% of Mexico's GDP. Remittances are the largest source of foreign exchange after manufacturing exports and petroleum. They are disproportionately important for rural communities in southern Mexico (Oaxaca, Chiapas, Guerrero), where they support household consumption, education, health, and small business formation.

Spatial pattern. Mexican migrants are concentrated in California (approximately 37%), Texas (approximately 23%), Illinois, and Arizona, reflecting proximity to the border and established diaspora networks that reduce migration costs and risks.

Case Study: The Philippines

The Philippines is one of the world's largest labour-exporting countries. Approximately 10 million Filipinos (approximately 10% of the population) live and work overseas, collectively known as Overseas Filipino Workers (OFWs).

Drivers. Structural factors include limited domestic employment opportunities (unemployment and underemployment rates exceed 5% and 15% respectively), low wages in many sectors, and a culture of migration reinforced by decades of overseas employment. The government actively promotes labour export through the Philippine Overseas Employment Administration (POEA), which regulates recruitment agencies and provides pre-departure training.

Destinations. OFWs are distributed globally, with major concentrations in the Middle East (approximately 2.5 million, primarily in Saudi Arabia, UAE, and Qatar), the USA (approximately 4 million, including permanent migrants), Southeast Asia (Singapore, Hong Kong, Malaysia), and Europe.

Remittances. OFW remittances exceeded USD 36 billion in 2023, representing approximately 9% of the Philippines' GDP. Remittances are the largest single source of foreign exchange and have supported macroeconomic stability, household consumption, and educational investment.

Social costs. Family separation (OFWs typically work abroad for 2--5 year contracts, leaving spouses and children behind); vulnerability to exploitation and abuse (particularly among domestic workers in the Middle East); deskilling (professionals such as nurses and teachers working in lower-skilled occupations abroad); and the creation of a "migration culture" that normalises family separation.

Common Pitfalls: Overgeneralising Migration Impacts

Migration impacts are not uniformly positive or negative for either origin or destination. The effects depend on the specific context: the type of migration (skilled vs unskilled, permanent vs temporary), the sectors involved, the scale relative to the destination population, the institutional and regulatory framework, and the characteristics of the migrants themselves. For example, brain drain is a concern for small, poor countries that lose a large proportion of their skilled workforce (e.g., Ghana, which has more doctors working in OECD countries than in Ghana itself), but is less significant for large countries where emigration is a small fraction of the total skilled workforce. Similarly, the fiscal impact of immigration depends on the age, skill level, and employment status of migrants. Always evaluate impacts with reference to specific evidence and case studies.

For related topics, see ./demographic-transition-model and ./population-policies. The parent topic page is at ../population-distribution.