||Permanent or semi-permanent change of residence by an individual or group of people. Migration has been enormously influential in determining cultural and social change at all scales, not least the global, and may be fundamental to individual experience.
Geographers have devoted much more attention to the study of migration than to other branches of population study. The collection of statistical data on migration requires a boundary of some sort to have been crossed and a certain length of time to have been spent over that boundary in a new area of residence. The range of migration studies has broadened considerably in recent years to include not only statistical estimates and models but also an appreciation of the impact of migration on places of origin and destination and on the individual. Migration is a key element of behavioural geography and attempts to understand the meaning and experience of migration for individuals involve the use of qualitative as well as quantitative sources. The process of migration is fundamental to the existence of diasporas. Migration may be a key element in understanding sense of place, community and Identity and for that reason migration studies have been reinforced in recent years as an exciting ingredient in population and social geography.
Migration, together with fertility and mortality, is a fundamental element determining an area\'s population growth and structure (see age and sex structure). Gross migration includes all flows; net migration the balance of moves into and out of an area. mobility is a rather more general term than migration, covering all kinds of territorial movements of whatever distance, duration or degree of permanence. A distinction is sometimes drawn between migration and circulation, a term given to short-term, repetitive or cyclical movements. Reviewing the whole process of mobility in history, Wilbur Zelinsky (1971) developed the idea of the \'mobility transition\', related to the general model of the demographic transition, in which he hypothesized a relationship between different types of movement and general processes of urbanization, industrialization and modernization in space and time (see also Potts, 1990; Segal, 1993; Skeldon, 1997). Zelinsky thus related five principal types of migration (international, frontierward, rural-urban, urban-urban and intra-urban, and circulation) to five types of society (pre-modern traditional, early transitional, late transitional, advanced and superadvanced). Changes in intensity of the different migrations were in turn linked to the changes in birth, death and population growth rates associated with the demographic transition.
Migration is an important ingredient in the process of globalization and has been for many centuries through, for example, the operation of the slave trade or through the mass trans-Atlantic migrations of the nineteenth century (Moch, 1992; Hatton and Williamson, 1994; Hoerder and Moch, 1996; see slavery). Migration may also be a crucial symptom of relations of dependence between different regions at different times. Equally, there has been a continuing interest in the global significance of migration (Potts, 1990; Castles and Miller, 1993; Skeldon, 1997) and its history (Moch, 1992; Hoerder and Moch, 1996).
scale provides an essential criterion for classifying migrations, as specified above. Other classificatory criteria include time (temporary/ permanent); distance (long/short); decision-making (voluntary/forced: see also refugees); numbers involved (individual/mass); social organization of migrants (family/clan/individuals); political organization (sponsored/ free); causes (economic/social); and aims (conservative/innovative). Different aspects of migration flows are also distinguished: stepwise migration generally implies movement through a series of places, e.g. from a village up the urban hierarchy; the related idea of chain migration links flows to established kinship ties between, for example, rural areas and the city; and return migration to the migrants\' origin is a feature of many streams. The further notion of circulation draws attention to the fact that not all migrations can be neatly classified into permanent movements and that some migration systems depend upon continuous, circular, flows (for seasonal work in agriculture and tourism, for example).
Given the great variety of migrations, it is not perhaps surprising that there is no comprehensive theory of migration. Nevertheless, successful attempts have been made to integrate migration into economic and social theory, spatial analysis and behavioural theory and the body of theory available across the relevant disciplines is now quite substantial (Ogden, 1984). In the late nineteenth century, E.G. Ravenstein formulated what he called \'laws of migration\' on which much subsequent work has been based (see Grigg, 1977). These were:
(a)Â the majority of migrants go only a short distance;(b)Â migration proceeds step by step;(c)Â migrants going long distances generally go by preference to one of the great centres of commerce or industry;(d)Â each migration current produces a compensating counter-current;(e)Â the natives of towns are less migratory than those of rural areas;(f)Â females are more migratory than males within their country of birth, but males more frequently venture beyond;(g)Â most migrants are adults â€” families rarely migrate out of their country of birth;(h)Â large towns grow more by migration than by natural increase;(i)Â migration increases in volume as industries and commerce develop and transport improves;(j)Â the major direction of migration is from the agricultural areas to the centres of industry and commerce;(k)Â the major causes of migration are economic.These \'laws\' have been modified by subsequent research rather than fundamentally disproved.
Geographers have traditionally paid considerable attention to distance-decay relationships in migration patterns. Most studies show the volume of migration to be inversely related to distance and HÃ¤gerstrand and others have used regression techniques to describe this relationship, the basis of the idea of the mean information field. In his formulation of the gravity model, Zipf (1949) demonstrates the relationship between population size, distance and migration. S.A. Stouffer (1940) refined this further by showing that migration was determined by opportunities at origin and destination and by intervening opportunities between the two. Others provided more elaborate multivariate models, relating distance to a variety of other factors (Stillwell and Congdon, 1991) and seeing migration as a component in population accounts.
A more general theory of migration was propounded by Lee (1966), who refined the idea of migration between two places as a response to various \'pushes\' at origin and \'pulls\' at destination. Another much-quoted effort sought to diminish the simple dualism of origin and destination and instead see migration in terms of a system of interlocking and mutually dependent forces, an idea developed in the first instance with reference to rural-urban migration in the developing world (Mabogunje, 1970). The wider understanding of migration flows owes much also to theoretical perspectives from neo-classical economics where migration is seen as a response to differences in wage and income levels in different locations. Thus migrants may move from low-wage, high-unemployment regions to high-wage, low-unemployment regions and bring about an equilibrium between the two. A rather different perspective derives from political economy: migrants are seen as an integral part of the working of the capitalist system and reflect capital\'s search for cheap and exploitable labour. Migration flows may reflect the changing spatial division of labour. There is also, however, an increasing awareness that migration needs to be understood not only in terms of economic causation but also as a social process, in relation to, for example, changing family and gender relations or changing longevity. Geographers have also begun to use ideas from structuration theory in order to bridge the gap between the individual and wider structures.
Research has concentrated on both empirical and theoretical aspects of the economic and social causes and consequences of migration; its selectivity by age, sex, marital status, ethnicity, education, occupation and stage in the life course; and behavioural aspects of the decision to migrate. Recent developments have emphasized the importance of mixed methods â€” combinations of quantitative (for example, the population census) and qualitative sources (for example, in-depth interviews, biographies or creative literature; see King, Connell and White, 1995) â€” to grasp the full significance and meaning of migration for the individual. Issues such as gender (Chant, 1992), refugees (Black and Robinson, 1993), migration of the highly-skilled (Salt, 1992) and migration policy (Kritz, Lim and Zlotnik, 1992; Kubat, 1993) have also come to the fore, as have the complex links between internal migration and, for example, gentrification and counterurbanization (Champion and Fielding, 1992; Stillwell, Rees and Boden, 1992; Geyer and Kontuly, 1996). Studies continue to cover a very broad geographical terrain (see, for example, Skeldon, 1990; King, 1993; Cohen, 1995; Hugo, 1996).Â (PEO)
References and Suggested Reading Black, R. and Robinson, V. 1993: Geography and refugees: patterns and processes of change. London: Belhaven.Â Boyle, P., Halfacree, K. and Robinson, V. 1998: Exploring contemporary migration. Harlow: Longman.Â Castles, S. and Miller, M.J. 1993: The age of migration. International population movements in the modern world. Basingstoke: Macmillan.Â Champion, A. and Fielding, A., eds, 1992: Migration processes and patterns, volume 1: Research progress and prospects. London: Belhaven.Â Chant, S., ed., 1992: Gender and migration in developing countries. London: Belhaven.Â Cohen, R. 1987: The new helots. Migrants in the international division of labour. Aldershot: Gower.Â Cohen, R., ed., 1995: The Cambridge survey of world migration. Cambridge: Cambridge University Press.Â Geyer, H.S. and Kontuly, T.M., eds, 1996: Differential urbanisation. Integrating spatial models. London: Arnold.Â Grigg, D.B. 1977: E.G. Ravenstein and the \'laws of migration\'. Journal of Historical Geography 3: 41-54.Â Hatton, T.J. and Williamson, J.G. 1994: Migration and the international labour market 1850-1939. London: Routledge.Â Hoerder, D. and Moch, L.P., eds, 1996: European migrants. Global and local perspectives. Boston: Northeastern University Press.Â Hugo, G. 1996: Research review 3: Asia on the move: research challenges for population geography. International Journal of Population Geography 2 2: 95-118.Â King, R., ed., 1993: Mass migration in Europe. The legacy and the future. London: Belhaven.Â King, R., Connell, J. and White, P., eds, 1995: Writing across worlds; literature and migration. London: Routledge.Â Kritz, M.M., Lim, L.L. and Zlotnik, H., eds, 1992: International migration systems. A global approach. Oxford: Clarendon Press.Â Kubat, D., ed., 1993: The politics of migration policies. Settlement and integration. The first world into the 1990s. New York: Center for Migration Studies.Â Lee, E.S. 1966: A theory of migration. Demography 3 1: 47-57.Â McNeill, W.H. and Adams, R.J. 1978: Human migration: patterns and policies. Bloomington, Ind. and London: Indiana University Press.Â Mabogunje, A.L. 1970: Systems approach to a theory of rural-urban migration. Geographical Analysis 2 1: 1-17.Â Moch, L.P. 1992: Moving Europeans. Migration in western Europe since 1600. Bloomington and Indianapolis: Indiana University Press.Â Ogden, P.E. 1984: Migration and geographical change. Cambridge: Cambridge University Press.Â Potts, L. 1990: The world labour market. A history of migration. London: Zed Books.Â Salt, J. 1992: Migration processes among the highly skilled in Europe. International Migration Review 26 2: 484-505.Â Segal, A. 1993: An atlas of international migration. London: Hans Zell.Â Simon, G. 1995: GÃ©odynamique des migrations internationales dans le monde. Paris: Presses Universitaires de France.Â Skeldon, R. 1990: Population mobility in developing countries: a reinterpretation. London: Belhaven.Â Skeldon, R. 1997: Migration and development: a global perspective. Harlow: Longman.Â Stillwell, J. and Congdon, P., eds, 1991: Migration models: macro and micro approaches. London: Belhaven.Â Stillwell, J., Rees, P. and Boden, P., eds, 1992: Migration processes and patterns. Volume 2. Population redistribution in the United Kingdom. London: Belhaven.Â Stouffer, S.A. 1940: Intervening opportunities: a theory relating mobility and distance. American Sociological Review: 845-67.Â Weiner, M. 1995: The global migration crisis. Challenge to states and to human rights. New York: HarperCollins.Â White, P.E. and Woods, R.I., eds, 1980: The geographical impact of migration. London: Longman.Â Zelinsky, W. 1971: The hypothesis of the mobility transition. Geographical Review 61: 219-49.Â Zipf, G.K. 1949: Human behavior and the principle of least effort. New York: Hafner.