Human migration involves the movement of a person (a migrant) between two places for a certain period of time. It is often considered a permanent relocation, as compared with temporary spatial mobility, which includes all kinds of movement by people, such as commuting, circulating, visiting, shopping, and temporarily working away from home.
This entry first details the most significant forms of migration according to their differing patterns and geographical scale. Next, migration decision making and the ever-changing dynamic processes of migrant behavior are examined. Last, the entry reviews some major constructs that migration scholars have presented as theoretical explanations of this constantly changing livelihood strategy of human mobility.
Internal migration within national political boundaries has always been the largest kind of population redistribution enumerated since demographic statistics have been collected and compared at global scales. Its character is often differentiated by the source and destination regions of such internal flows. Hence, rural-to-rural migration, rural-to-urban migration, urban-to-rural migration, and urban-to-urban migration can each feature in an internal migration system of population transfers and exchanges between these geographic places.
Shorter-distance changes of residence that do not cross the definable boundary of a place (e.g., a city) are more generally referred to as residential mobility, and within urban realms, it is common to distinguish between interurban migration and intra-urban residential mobility. Further differentiations within this group of internal migration streams and counterstreams might be characterized by the growth of megacities, or global cities, in which rapid urbanization occurs within national urban hierarchies. The accelerated growth of these large conurbations in countries of the global South occurs as a consequence of in-migration from rural and urban sources and the accompanying fertility increases of the inmigrant populations. Indeed, the 20th century witnessed the rapid urbanization of the world's population, which in 2009 stands at more than 6.7 billion.
Migrants who cross national borders are said to undertake international migration. Immigration is a relatively permanent move into a different country from the migrant's home, whereas emigration is the relatively permanent move out of the home country. In contemporary times, such international “cross-border” movements can take on a more complex character, with migrants living “betwixt and between” two “life-worlds,” experiencing and practicing transnational migration, undertaking repetitive mobilities, maintaining close social contacts, and building multilocal, transnational networks of kith and kin.
With increasing globalization, rates of international migration have grown in recent years. In 2006, there were 191 million international migrants in the world, with this estimate representing more than a twofold increase from 76 million in 1960. Whereas many countries are now “sending sources” of international migration, relatively few countries are the targeted hosts of immigration streams, and since immigration policies invariably restrict and control entrance to these receiving countries, migrants have long sought irregular means of entry and access to work “across borders.” Most, however, pursue legal means of entry, including short- and long-term sojourning, the acquisition of visas for study, educational advancement and work permission, and often lengthy legal immigration and permanent residence petitioning and asylum petitioning. Irregular migration is the currently acceptable label for those undertaking nonlegal means of entry, replacing the plethora of xenophobic labels that have commonly been used in many a contentious anti-immigration debate, such as “illegals,” “illegal aliens,” “undocumented,” “unauthorized,” “overstayers,” “clandestine entrants,” “failed asylum seekers,” and “unwanted foreigners.”
Migration can also be differentiated according to the conditions that prompted the decision to move away from the migrant's original place of residence, with a dichotomous categorization distinguishing a move as either voluntary or involuntary, “forced” migration. Voluntary migration is often economically driven, is selective by age and resource endowment, and includes the whole range from unskilled workers to highly skilled workers seeking better opportunities, experiences, and incomes in more distant labor markets than the ones they can access by staying in their original homes (including commuting and temporary work off-farm or in nearby urban centers). Voluntary migration is also a decision made and undertaken collectively by migrants and partners, migrant families, and selected members. On the other hand, the migrant's dependants—infants, young children, female partners—who are “tied movers” can be considered to be migrating involuntarily if not involved in the decision making by the household head or patriarch. In short, the social (and gendered) contexts of family power relationships often intervene in decision making concerned with the migration of families and family members.
Certain historical and more contemporary explanations of voluntary and involuntary migration amply demonstrate the richness of explanations of human migration as both historical and spatial contexts vary and change, thereby rendering this mobility option extremely flexible, ever changeable and changing. There is now a growing consensus that multiple theoretical explanations reign, not one all-encompassing single theory, though the pathway to this holistic generalization has been built on many informative constructs, with some of the most exemplary detailed below.
In the late 18th century, Ernest George Ravenstein used mixed methods of analysis to inductively generate a series of “laws of migration” that attempted to explain and predict migration patterns both within (internal migration) and between (international migration) nations. Two concepts, absorption and dispersion, were derived to explain county increases and decreases, respectively, as Britain went through its urban-industrial transformation during the second half of the 19th century. Ravenstein's first paper in 1885 proposed seven “laws of migration” or generalizable regularities in internal patterns of movement: (1) most migrants only proceed a short distance and toward centers of absorption; (2) as migrants move toward absorption centers, they leave “gaps” that are filled up by migrants from more remote districts, creating migration flows that reach to “the most remote corner of the kingdom”; (3) the process of dispersion is inverse to that of absorption; (4) each main current of migration produces a compensating countercur-rent; (5) migrants proceeding long distances generally go by preference to one of the great centers of commerce or industry; (6) the natives of towns are less migratory than those of the rural parts of the country; and (7) females are more migratory than males. Several of these original seven laws included assertions that were later considered “additional laws of migration”; (8) most migrants are adults; (9) large towns grow more by migration than by natural increase; (10) migration increases in volume as industry and commerce develop and transportation improves; (11) the largest volume of internal migration is rural-urban migration; and (12) the major determinants of migration are economic forces.
This view should remind us that internal migration became an adaptive strategy for rural people in the past centuries, as their agrarian livelihoods were transformed. Ravenstein's “laws,” however, did not explain why some rural adults would move while others would not. For this, Guy Standing's conceptual explanation is insightful.
Standing proposed that four conditions needed to exist to make peasants in traditional communities become migrants, the conditions being reflected in the decay in the traditional mode of exploitation (i.e., feudalism): (1) migration must exist as an acceptable response to adversity or frustrated aspirations; (2) peasants come to identify their condition as neither just nor inevitable, because some reciprocal relationship between them and their feudal landlords has been violated; (3) staying and instigating a revolt is seen as having a minimal chance of success, because the peasants are not organized in their objection to oppression, violence, or economic threats and they lack communal strength and unity; and (4) peasants come to reject customary forms of exploitation because of a growing sense of deprivation and despair that things won't get better and because of increases in their disadvantageous position in contrast to their previous situation.
Changing the scale from internal to international mobility, Douglas Massey, in a commentary on Mexican international migration and development relations, developed an interesting theoretical construct to explain the prevalence of emigration in developing countries. Three structural conditions were said to characterize the development process: (1) the cyclical nature of industrial expansion in urban areas, paired with the more or less constant pressure for outmigration from rural areas, determined by capital formation, enclosure, and market creation, which together destroy the basis of peasant social organization and weaken their ties to rural communities; (2) discontinuities in economic growth across time and space (i.e., uneven geographic distributions within countries and between countries), producing cyclical constrictions of opportunity in developing urban economies paired with expansions of opportunities in growing (metropolitan/core) economies abroad; and (3) declining real costs of transportation and communication, actualized by increasing access to reliable and affordable systems.
Discussing the dynamic deepening of the Mexico-U.S. migration system, Massey also explained why there is a tendency for international emigration to become progressively independent of the economic conditions that originally caused it, referring to this maturing of the migration system as the result of cumulative causation. Three mutually reinforcing processes appear to be at work in this transformational dynamic: (1) transnational network formation; (2) agrarian transformation, via emigrant earnings, remittances, and returnee “demonstration effects”; and (3) the evolution over time of deprivation and impoverishment in source communities.
Now, finally, returning to forced migration, this label has become a suitable categorization of a range of global movements in which an element of coercion exists, including threats to life and livelihood arising from biophysical or social/anthropogenic crises—environmental disasters, chemical or nuclear disasters, famine, civil war, genocide, or development-induced displacement. Natural disasters, environmental degradation and destruction, warfare, civil strife, banditry, warlord enmity, genocide, and every imaginable horror brought about by military power struggles and the accompanying “collateral damage,” which threatens and kills local civilian populations, are contemporary forces instigating and perpetuating such involuntary, forced migrations. Refugees, asylum seekers, internally displaced persons (IDPs), and development-induced and environmental-disaster-displaced persons are some of the main groups forced to flee their homelands and seek asylum beyond their nation's borders. A majority of these displaced persons and refugees are the rural poor and powerless in the global South—Africa, Asia, and Latin America—who have consistently suffered from disruption, destruction, and displacement in recent decades.
A growing practice among international criminal groups, syndicates, and organizations is to profit from such forced migration by ushering in a new form of slavery and coercion in which the migrants are treated as disposable commodities. These underground organizations prey on young women and children by offering hope, while tricking, brutalizing, and selling them into prostitution and sex working, sweatshop labor, and similar illicit, dehumanizing and/or dangerous occupations in which they have little autonomy or basic rights and human dignities. The International Labour Office has recently estimated that at least 12 million people work as slaves or in other forms of forced labor and as many as 2.5 million are in forced labor as the result of cross-border trafficking, with approximately half being employed against their wills in sex trafficking.
Commuting, Gravity Model, Immigration, Mobility, Rural-Urban Migration
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