Migration is the crossing of a boundary in search of work and/or residence for a certain minimum period of time. It includes the movement of refugees, displaced persons, uprooted people as well as economic migrants. Internal migration refers relocation from one area (a province, district or municipality) to another within one country while international migration is a territorial relocation of people between nation states. Two forms of relocation can be excluded from this broad definition: first, a territorial movement which does not lead to any change in ties of social membership and therefore remains largely inconsequential both for the individual and for the society at the points of origin and destination, such as tourism; second, a relocation in which the individuals or the
groups concerned are purely passive objects rather than active agents of the movement, such as organised transfer of refugees from states of origins to a safe haven.
The Penguin Dictionary of Human Geography defines a migrant as ‘a person who moves voluntarily from one country to another for purposes of permanent residence. That person is an emigrant from his native country and an immigrant into a new country’. Migration is probably a more important element in determining population structure and change in an area than fertility and mortality. The volume of migration or gross migration includes all migration flows into and out of an area, whereas net migration, the balance of migration, is the difference between the in and outflows for an area. Centripetal migration in which people move towards population centres from the surrounding countryside, has been distinguished from the centrifugal migration, in which people disperse outwards from central cities into the surrounding towns and villages. On a time scale, migration may be temporary or permanent. Temporary movement may take the form of seasonal migration, usually of agricultural workers, to meet a demand during labour-intensive seasons or periodic migration, of workers away from their permanent homes for several years during which they send home remittances, and in more developed societies middle-run migration and the inter-metropolitan circulation of elites may be important.
The phenomenon of migration has been classified into various types on the basis of motivation, distance and time. On the basis of motivation, migration has been classified as social and economic. Based on distance, migration falls into two groups, i.e. long distance and short distance. The time factor makes the divisions into ancient, historic and recent. When the time and frequency of migration are considered, migration can be classified into daily, seasonal, semi-permanent and permanent types. Similarly, when the spatial parameter is taken into consideration, migration is either internal or international. Internal migrations are further sub-divided in rural-urban, urban-rural, urban-urban and rural-rural areas. Migrations, both past and present, are both voluntary and forced types.
In addition, migration movements may be classified on the basis of the reasons behind the movement, e.g. voluntary or forced, sponsored or free, for conquest or colonisation, whether impelled by idealistic or economic factors. Thus in innovative migration people migrate as a means of achieving something new, whereas in conservative migration they move in response to a change in conditions in order to retain what they had. Betterment migration is similar to innovative in that a person moves to improve his position, but suggests that push factors at the place of origin are less important than the pull of the destination.
Many efforts have been made to explain the patterns of migration. One of the pioneering researches has been done by E.G. Ravenstein as early as in 1880s. In his paper ‘The Laws of Migration’ he presented 8 principles:
- The great body of migrants only proceed a short distance and consequently there takes place a universal shifting or displacement of the population, which produces ‘currents of migration’ setting in the direction of the great centres of commerce and industry which absorb the migrants.
- Migration occurs in a series of stages. There is a process of absorption, whereby inhabitants immediately surrounding a town of rapid growth flock into it; the gaps thus left by the rural population are filled up by the migrants from more remote districts, and so on until the attractive force of a rapidly growing city is spent.
The process of dispersion is the inverse of that of absorption and exhibits similar features.
- Each mainstream of migration produces a compensating counter current.
- Migrants proceeding long distances generally go by preference to one of the great centres of commerce and industry.
- The natives of towns are less migratory than males over short distances.
Females are more migratory than males over short distances.
The incidence of migration increases with increasing technological development.
Further studies have used more sophisticated mathematical forms to explain the migration patterns. The ‘Inverse Distance Law’, expounded by G K Zipf is one such attempt. He states ‘ the volume of migration is inversely proportional to the distance traveled by the migrants’. The mathematical expression is as follows:
Where Nij is the number of migrants from town i to j and Dij the distance between the two towns.
Against the common perception that there is no overall theory of migration, a number of studies have not only examined the relationships between volume of migration and distance, but also have considered the influence of ‘opportunities’. S Stouffer proposed the ‘Theory of Intervening Opportunities’, in which he suggested that ‘the number of persons going a given distance is directly proportional to the number of intervening opportunities’.
Where Nij is the number of migrants moving from town i to j, Oj the number of opportunities at j, and Oij the number of opportunities between I and j.
Stouffer defined ‘opportunity’ in terms of vacant houses, but others have interpreted it in terms of employment opportunities. Stouffer later refined his model by the addition of another variable, that of ‘competing migrants at destination.’ Many recent studies of migration have tended to accept a general background of ‘push-pull’ factors, but also pointed out that any migration flow may also be interpreted as the aggregate result of numerous personal decisions about whether or not to move, when to move, and choice of destination. D J Bogue has discussed migration-stimulating situations and examined the factors influencing choice of destination.
Inputs from The Penguin Dictionary of Human Geography by Brian Goodall and Human Geography by R Knowles and J Wareing.