Theories of Migration: Why Do People Migrate?

Migration can be international or domestic, voluntary or forced. In all cases, it is a complex process shaped by individual decisions and family strategies. Labor markets, state rules, and social conditions also set the routes people can use and the risks they face. Traditionally, scholars treated migration as a consequence of geographical differences between regions, especially differences in work and income. Quality of life, political freedom, environmental stress, and existing migrant communities can also shape the decision to move. By the end of the nineteenth century, social scientists had begun to ask why people migrate, and they developed several explanations. These are the main theories that try to make sense of the causes of migration:

• Push-pull theory: It claims regions have conditions that make people either immigrate to them or emigrate from them.
• Neoclassical theory: It claims people migrate to regions where the labor market is in need of workers, or to regions where the market better rewards their own abilities.
• Globalization theories: They claim migration may or may not be encouraged by the process of globalization.
• Dual labor market theory: It claims two kinds of people migrate to developed economies — both high-income and low-income workers.
• New Economics of Labor Migration (NELM) theory: It claims the decision to migrate is one made by entire families rather than individual people.
• Diaspora theory: It claims members of ethnic or national groups spread around the world, yet maintain close contact with one another abroad.
• Migration network theory: It claims migrants develop support networks that encourage other people to migrate too.
• Migration systems theory: It claims migration is a process that has bi-directional flows, affecting both origins and destinations of migrants.
• Migration transition theory: It claims migration varies with the level of development of a region.

Push-Pull Theory

The push-pull theory treats migration as a response to conditions that make one place difficult to remain in and another place more attractive.

Some of them are:

• Political pressures: People flee regions experiencing violent conflicts, civil wars, rising crime or political instability.
• Economic incentives: People move in search of better jobs.
• Cultural ties: People move to regions where they feel welcome, such as places where their native language is spoken.
• Environmental pressures: People flee natural disasters, such as earthquakes, or gradual environmental processes, such as sea level rise.
• Demographic pressures: People move from densely inhabited regions to places where there is less strain on public services and city traffic.

In the nineteenth century, Anglo-German geographer Ernst Ravenstein claimed that the primary cause for migration was economic. Over the following years, several scholars challenged his argument. Some authors connected migration to distance between regions. Others stressed population size or the relative strength of local economies. In 1966, Everett Lee added that migration depends on push-pull pressures, obstacles to movement and the individual willingness to migrate.

The problem with push-pull models is that they are largely descriptive.

They consider many drivers of migration, but they do little to explain the relationships among those drivers.

They also struggle to explain why the same region can attract some migrants and repel others, or why some migrants later return to their places of origin.

Neoclassical Theory

Like its counterpart in economics, the neoclassical theory of migration is based on the idea of equilibrium. In this view, immigration and emigration balance one another in the long run. In general, adherents of this theory believe that migration is explained by geographical differences in labor markets.

In neoclassical theory, people move from regions with surplus labor to regions where workers are scarce and wages are higher.

This process makes wages increase in the source region and reduce in the destination region. Eventually, an equilibrium point is reached, and wages end up being exactly the same in both regions.

In 1970, John Harris and Michael Todaro drew inspiration from the neoclassical school of thought in order to create the Harris-Todaro model.

The model tries to explain rural-urban migration. Harris and Todaro were especially concerned that rural populations continued to move to cities even when urban jobs were increasingly difficult to find. In their model, rising urban unemployment does not automatically stop rural migration because potential migrants compare the expected urban wage with the rural wage. If the expected payoff remains higher in the city, rural workers still have an incentive to migrate.

Accordingly, rural exodus can continue as long as the wage difference outweighs the risk of unemployment.

Another strand of neoclassical thought is human capital theory, developed by authors such as Larry Sjaastad in 1962. He argued that people have different skills and knowledge, and that the value of this “human capital” can vary between regions. In developing countries, for example, specialized engineers may struggle to find jobs that match their qualifications. Some end up in the gig economy, including as drivers for ride-hailing platforms. According to this theory, people have an incentive to migrate when they believe other labor markets will reward their abilities more.

One example is younger workers who are better educated than the local labor market can absorb and therefore expect higher salaries elsewhere.

Neoclassical theories of migration are usually criticized for their assumptions.

They assume that people are rational, that they have reliable information about wage differences between regions, and that migration is not blocked by major obstacles. In practice, accurate wage information may be hard to obtain. Even with that information, people may decide to stay because of family ties or risk aversion. Identity and attachment to place can also outweigh a wage calculation. Real migration also faces legal, physical, and social obstacles. In developed countries with better-paid labor markets, these obstacles can include visas and border checks. Border walls and xenophobia can add further barriers.

Globalization Theories

Globalization is the process by which the world becomes more integrated, with people, companies and governments engaging in ever-increasing flows and interactions. This process can be seen either positively or negatively.

In a globalized world, migration is shaped by opposing pressures:

• Improvements in communication and transportation technologies make migration easier, even when states preserve political barriers to entry. From a distance, people can see how life is elsewhere and can use mature sea, air, and land routes to move.
• The same technologies can reduce the need for permanent migration. People may travel temporarily, commute between cities, or work abroad for a limited period before returning to their original place of residence.

For instance, many people engage in pendular migration: regular movement between one’s residence and workplace, often in different cities. Others use working holiday visas, which allow migrants to work in a foreign country for an extended but temporary period.

Marxist scholars of world politics, such as Immanuel Wallerstein, argue that globalization makes migration less dependent on the wishes of individual people. In their view, migration is a consequence of systemic interactions that reinforce global inequalities because highly educated workers often leave their home countries for developed economies. This logic appears in the way states facilitate migration for people with abundant money or scarce expertise, especially through “golden visas” or visas for people with extraordinary abilities. In the words of Polish sociologist Zygmunt Bauman, “The riches are global, the misery is local”.

One criticism of Marxist theories about the relation between globalization and migration is that skilled workers can improve their lives by migrating, even when their movement also reflects global inequality.

Dual Labor Market Theory

Michael Piore helped develop this approach in Birds of Passage: Migrant Labor and Industrial Societies, published in 1979.

Dual labor market theory argues that developed economies attract two different kinds of migrants because they need both highly paid specialist labor and low-paid service labor.

• Highly skilled workers: They are selected for their human capital or for belonging to a privileged elite. They usually have little difficulty obtaining visas and work permits, and their jobs are often well paid.
• Low-skilled workers: Rather than being selected through privileged channels, they migrate to perform complementary jobs such as janitorial work, retail work, customer service, domestic work, and agricultural labor. Some overstay visas or work without regular status.

This approach posits that low-skilled workers with irregular migration status serve both economic and political purposes. Irregular migrants are vulnerable to abuse by employers. Abuse can take the form of excessive working hours, wage theft, or unsafe working conditions. It can also involve physical violence, verbal violence, or debt bondage. These migrants form a compliant workforce that can be exploited to reduce costs. Certain politicians also benefit from the presence of irregular migrants. They can portray migrants as scapegoats for poor economic conditions and direct xenophobic hostility toward them, often helping far-right parties that promise to clamp down on migration.

In the Arab states of the Persian Gulf, for instance, the Kafala system has been used to monitor migrant laborers working in construction and domestic service. These workers are often subjected to exploitative working conditions because their migration status depends on their employers. Many foreign laborers in these countries have limited chances of upward mobility, yet the wage gap can still make the move preferable to conditions in their countries of origin.

New Economics of Labor Migration (NELM) Theory

The NELM theory of migration emerged in the late 1970s, thanks to the studies of scholars such as Oded Stark.

This perspective treats migration as a family decision.

It is a theory with ties to anthropology and sociology because it examines how poor families try to improve their lives even under inequality and adversity.

Proponents of the NELM theory identify several reasons why families decide to migrate:

• Migration is a way to diversify the work of the members of the family, so that a crisis in a given place or economic sector will not make all relatives worse off. Thus, people might migrate even if it means not increasing their salaries — after all, just diversifying sources of income might be valuable.
• Migration is a way to help family members raise enough money to sustain the family business.

Accordingly, many migrants who move to well-paid jobs in other regions send remittances back home. Recent World Bank material shows the scale of that dependency: in Tajikistan, remittances were about 49% of gross domestic product (GDP) in 2024, while a World Bank remittance brief estimated Tonga at about 38% of GDP for 2024.

• Migration is a way to deal with relative deprivation: the circumstance in which a family has enough money to move elsewhere, and knows that, in doing so, the prospects for the family are likely to improve.

NELM theories have been criticized because they see families as a “black box” — meaning that they neglect the dynamics that take place within each family. For instance, migration might be a way for children to gain independence from their fathers, or for women to escape from abusive husbands. Also, in some cases, families might split apart because elders are unwilling to leave their homes while younger people wish to find better jobs in a different place.

Diaspora theory

As a general rule, a diaspora is a population that has become scattered around the world after being displaced by force. The concept has been applied to African slaves sent to American and Asian colonies. It has also been applied to Jews who fled Nazi Germany.

Nowadays, in ordinary speech, a diaspora refers to any transnational community that shares certain characteristics. South African sociologist Robin Cohen described those characteristics in Global Diasporas:

• The community is present in many different states.
• The community migrated either by force or in search of business or colonial opportunities.
• The members of the community share a certain collective memory.
• Within each foreign country, the members of the community share a sense of solidarity among themselves and engage in communal activities.

Proponents of the diaspora theory, such as Alejandro Portes, argue that a diaspora can emerge from encouragement by governments, colonial companies or migrants themselves.

However, authors such as Luis Eduardo Guarnizo have claimed that diasporas initiated by migrants themselves are rare, and that relations between members of a diaspora are greater within privileged classes.

Migration Network Theory

The migration network theory focuses on the interactions between migrants within a region and between them and those who remained in the source regions.

Migration network theory proposes that migration may begin because of a structural shock but then continue because networks reduce the costs and risks of moving.

For example, a rise in unemployment or a natural disaster might lead people to look for another place to call home, and their presence elsewhere might give rise to a migratory network that incentivizes others to migrate and reduces costs and risks involved in doing so.

In developed countries such as the United States and those that form the European Union, experienced migrants often help new arrivals settle in. They may help them find a home, apply for jobs and open a bank account. They may also help with bureaucratic procedures. Experienced migrants may be asked to invite new workers to their workplaces in order to meet growing demand for labor. Furthermore, specialized companies can create or maintain migratory networks by offering services such as visa facilitation. These companies are known as the “migration industry”. All of these cases highlight the impact of network effects on migration.

Migration Systems Theory

While many, if not most, migration theories emphasize the consequences of migration for destination regions, the migration systems theory looks at the reciprocal effects that migrants produce in places of origin and destination.

In 1970, Nigerian geographer Akin Mabogunje presented a comprehensive study of rural-urban migration in Africa, but his ideas can also be extrapolated to international migration. He argued that migrants who were welcomed and found a better life elsewhere sent positive information back to friends and relatives who had stayed in their places of origin.

In Mabogunje’s account, positive information flowing from destinations to origins makes more people want to migrate.

Furthermore, these people usually want to migrate to specific places that they regard as the best destinations.

Other authors have elaborated on Mabogunje’s ideas, particularly two American sociologists.

Peggy Levitt argued that migrants generate so-called “social remittances” — flows of ideas and identities that arrive in certain regions and change people’s aspirations.

Ultimately, she claimed, people would no longer be satisfied with their current lives, because there are better lives elsewhere.

Likewise, Douglas Massey used the concept of “cumulative causation” to argue that migration engenders socioeconomic changes in places of origin. He believed that, if migrants were successful in their ventures, a “culture of migration” would emerge and more and more people would want to migrate.

The central argument of migration systems theory is that a certain flow from one region to another might bring about other flows, in both directions.

The main issue with these theories is that they fail to account for the rise and the decline of migration systems.

For example, most initial migrations from one place to another fail to create migratory systems. Nomadic movements show how movement can occur without producing a stable route. In addition, some consolidated migration routes might decline when they depend on natural resources that become depleted. Flows between mining towns and port towns, for instance, commonly become less intense as mineral reserves are exhausted.

Another issue is that these theories neglect the negative aspects of migration systems, which might be exclusivist or not be positive at all.

Certain Cuban communities in the United States, for example, are loath to welcome supporters of the Communist regime that rules their homeland. These people are actively discriminated against in terms of job offers in the informal economy. Besides that, migrants in general might be unwilling to support other migrants. After all, they may compete against one another for jobs and residences. They may also compete for relief aid or regularization of migratory status.

Migration Transition Theory

In 1971, American geographer Wilbur Zelinsky introduced the migration transition theory, under the influence of the demographic transition theory by Warren Thompson.

Migration transition theory links the intensity and direction of migration to a society’s level of urbanization and economic development. In simple terms, it describes the following phases of migration, with changes in patterns over time:

• In premodern societies, which are those that have not urbanized yet, there is little to no migration.

People are used to living always in the same place, and there is little hope for anything else, because communication and transportation networks are still inadequate for migration.

• In early transitional societies, which are those that are beginning to urbanize, migration increases substantially.

People suddenly have to deal with population growth, fewer rural jobs, and technological change. These pressures produce a large movement of people from the countryside to cities.

• In late transitional societies, which are those in which cities are more prominent than rural areas, urban-urban migration increases while rural-urban migration decreases.

At this phase, there are many cities competing with one another to attract the labor force, and only a few people remain in the countryside in order to support agriculture and livestock farming.

• In advanced and in super-advanced societies, nearly all migration is urban, and there is much more immigration than emigration.

People who live in such societies are not willing to move elsewhere, while people from less developed regions are more than eager to migrate to a better place.

The migration transition theory has been empirically supported in several settings, especially where urbanization and development expand mobility. Current global data also qualify the claim. The International Organization for Migration’s 2024 report, using UN migrant-stock data, shows that most international migrants live in very high-HDI countries, while the World Bank emphasizes that income gaps remain a major driver of movement. Development can therefore increase mobility. Rich destination countries still shape the largest migration corridors through wages and labor demand, as well as through visas and border controls.

Advocates of this theory must therefore keep in mind that the correlation between migration and development is neither inevitable nor irreversible.

Lebanon’s capital, Beirut, was once regarded as the “Paris of the East” because it was a desirable place to live. However, war and political instability devastated the country in the second half of the twentieth century.

Conclusion

Migration theories try to explain why people leave home and settle elsewhere. Early approaches emphasized the attributes of places, especially differences between labor markets. In the 1970s and 1980s, some theorists treated migration as a consequence of systemic interactions within capitalism. Their focus was on the way global inequality affects very low-paid and highly paid workers differently. More recent approaches emphasize social dynamics. NELM concentrates on family decisions, while diaspora theory and network theory examine the role of wider communities. Taken together, these perspectives show that migration is produced by incentives and constraints. Institutions, households, and social networks shape how those pressures become actual movement.