Migration is a generic term used to refer both to immigration (or in-migration) and to emigration (or out-migration). Formally, these terms may refer to various types of change of residence, but we customarily speak of immigration and emigration when the change of residence is between nations, and of in-migration and out-migration when the change of residence is between subunits of a nation. The term ‘net migration’ is used to denote the difference between the number of in-migratory events and the number of out-migratory events with respect to a particular geographic unit during a given time period.
Events of immigration (in-migration) and emigration (out-migration) constitute two of the four components of population change; the other two are births and deaths. For large areas, population change is generally determined predominantly by the balance of births and deaths (‘natural increase’). However, for small areas the net migration is often larger than the natural increase.
A migration stream is defined as the total number of migratory events from Place A to Place B during a given time period. The counterstream is defined as the total number of migratory events from Place B to Place A. The sum of events in the stream and counterstream is termed the gross interchange between A and B. The effectiveness of migration is defined as the ratio of the net migration between A and B and the gross interchange between the two places. Logically, therefore, the effectiveness of migration can vary from a low of 0 to a high of 1. For most pairs of geographic units the effectiveness of migration tends to be much closer to 0 than to 1.
Certain types of migration are commonly distinguished. Petersen (1975) made useful distinctions between the concepts of free, impelled and forced migration. In free migration, the will of the migrant is the main factor. In impelled migration, the will of the migrant is subordinated to the will of other persons. In forced migration, the will of other persons is paramount, and the will of the migrant is of no weight at all. Return migration is defined as migration back to a place in which one had formerly resided. For most individuals who have migrated several times during their lifetime, return migrations are an important component of the total number of movements. Chain migration refers to the common pattern whereby individuals migrate to a particular destination in which they already have kin or friends who have previously migrated from the individual’s own area of origin.
Migration differentials
It is universally observed that the propensity to migrate is strongest among young adults. Other differentials in migration tend to be limited to particular cultures or locales.
Determinants of migration
The determinants of migratory behaviour may conveniently be analysed in terms of a preference system; a price system; and the total amount of resources available for all goals (Heer 1975).
First, the preference system describes the relative attractiveness of various places as goals for potential migrants, compared to other goals which their resources would allow them to pursue. An area’s attractiveness is the balance between the positive and negative values which it offers. Among the most important of the positive values is the prospect of a better-paying job. Other advantages achieved by migration include the chance to live in a more favourable climate, freedom from persecution, marriage and the continuation of marital ties, and the desire for more adequate housing, a factor particularly important with respect to central city to suburb movements.
However, migration also creates negative values. A major disincentive to migration is that it involves a disruption of interpersonal relationships with kin and old friends. Chain migration is so attractive precisely because it mitigates this disruption of relationships. Other negative aspects of migration are the necessity to learn new customs and sometimes a new language. Laws restraining legal entry or departure are also, of course, important deterrents to migration.
Second, the price system describes costs in money, energy and time (which cannot be used in the pursuit of other goals) imposed by a given migration decision. As the cost of migration generally varies in direct proportion to the distance travelled, the number of migrants to a given place tends to vary inversely with the distance.
Third, the total resources available for all goals also affect the decision to migrate. If the only drawback to migration is the expense of the move, then an increase in monetary income should increase the probability of migration. The secular increase in monetary income since the end of the nineteenth century in the developed nations should have increased rates of migration, provided that the value and price of migration had remained constant. However, to the extent that regional differences in job opportunities may also decline, the factor of increasing resources may be offset.
Consequences of migration
Migration has consequences for the areas of net out-migration and net in-migration, as well as for the larger social system, which includes both the area of out-migration and the area of in-migration.
First, net out-migration may have several important consequences for an area. It may relieve population pressure and cause the average level of wage and salary income to rise. However, it may cause the value of land and real estate to decline. Areas of net out-migration incur the loss of the investments made to raise and educate those children who spend their productive years elsewhere.
Second, net in-migration may also have important consequences. If the area is definitely underpopulated, the resultant population increase may help the area achieve economies of scale and thus raise the general standard of living. Under other circumstances, net in-migration may result in decline in average wage and salary income. In either case, a net flow of in-migrants will tend to raise the price of land and real estate. It is also possible that a high rate of in-migration fosters social disorganization, as social-control networks are not easily established among persons who are strangers to one another.
Third, for the system comprising the areas of both net inflow and net outflow, migration promotes a redistribution of population. If migrants have been responsive to differences in job opportunities, this redistribution will further the economic development of the total system. Usually, migration also has consequences for the degree of regional homogeneity within the total system. Since migrants tend to move from low to high income areas, regional income inequalities are generally reduced by migration. Moreover, migration often helps to reduce regional disparities in racial, ethnic and religious composition.
Migration policies and legislation affecting migration
It is useful to distinguish between migration policies, which are intentionally designed to influence migratory flows, and legislation affecting migration which in fact influences the flow of migrants even though it is designed to serve some other major goal or goals. Almost all nations have adopted policies with respect to international migration. Most such policies severely restrict immigration, so that the actual stream of legal immigrants is much smaller than it would have been if no barriers had been imposed (Davis 1981). As a result, many nations, particularly the USA, have a large number of illegal immigrants. However, certain nations have actively encouraged immigrants of a particular type. Australia, for example, in the twenty-year period following the Second World War, actively sought to increase its population through subsidizing immigration from Europe while at the same time discouraging immigration from Asia. Although most governments proclaim the right of their citizens to emigrate, many of them place restrictions on emigration of selected persons for reasons of national security. Moreover, restrictions on emigration can be very severe, as exemplified until recently in the former Soviet Union.
The stream of rural to urban migration has marked every nation, both developed and less developed, since the beginning of the Industrial Revolution. In the developed nations, the net stream of rural to urban migration has in most cases ceased; in many of the less developed nations, it is still of considerable magnitude.
Explicit policies concerning internal migration are less common than with respect to external migration, but in most nations there is a large body of legislation which affects internal migration either negatively or positively. Nations which do have explicit policies regarding internal migration have generally tried either to discourage the growth of their largest cities or to encourage settlement of scarcely populated regions with important natural resources.
David M.Heer
University of Southern California
References
Davis, K. (1981) ‘Emerging issues in international migration’, International Population Conference, Manila, 1981, vol. 2, Liège.
Heer, D.M. (1975) Society and Population, 2nd edn, Englewood Cliffs, NJ.
Petersen, W. (1975) Population, 3rd edn, New York.
