International migration is a term used to refer to change of usual residence between nations. The number of international migrants is always much smaller than the total number of persons traveling across international frontiers, because the overwhelming majority of such travelers do not intend to change their usual residence. International migration is contrasted with internal migration, which refers to a change of usual residence within a nation. The term immigration is used to denote the flow of persons establishing a usual residence in a given nation whose last residence was in some other nation. The term emigration is used to denote the flow of persons relinquishing a usual residence in a given nation to establish residence in some other nation. Net international migration denotes the difference between the number of persons immigrating to a given nation in a given period and the number emigrating from that nation in the same period.
Immigratory and emigratory events constitute two of the four components of national population change; the other two components are births and deaths. For most nations, population change is determined predominantly by the balance of births and deaths (natural increase). However, for a few nations in certain periods, the net international immigration has also been an important component of the total population change.
In determining the number of persons who have changed residence among nations, national statistical agencies must specify the meaning of a change in usual residence. The United Nations (1978) suggests that international movements with an intended stay of more than one year be classified as international migration. Unfortunately, there is considerable lack of uniformity among nations with respect to how international migration is defined. For example, according to data of the Mexican government, some 46,000 Mexicans emigrated to the United States in 1973; according to data of the U.S. government, the number of permanent legal immigrants from Mexico was about 72,000 (United Nations 1978). Also, many governments, including that of the United States, collect data on immigration but not on emigration. Finally, all data on immigration published by governments refer to legal immigration only. Data on illegal or undocumented immigration cannot be tabulated.
Certain terms useful for the study of either international or internal migration will now be explained. A migration stream is defined as the total number of migratory events from place A to place B during a given time. 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. The effectiveness of migration can therefore 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.
Petersen (1975) makes very useful distinctions among the concepts of free, impelled, and forced migrations. 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. Another useful term is return migration, defined as migration back to a place in which one had formerly resided. Chain migration (MacDonald and MacDonald 1964) is also a frequently used concept. It refers to the common pattern whereby a given individual migrates to a particular destination in which he or she already has kin or friends who have previously migrated from his or her own area of origin.
It is universally observed that the propensity for international migration is strongest among young adults. Other differentials in migration tend to be limited to particular cultures or locales. Because the highest propensity for international migration is among young adults, the contribution of international migration to population change is often considerably greater than the net international migration by itself. This is because the birthrate for migrants is higher than for the total population, and the death rate is lower.
DETERMINANTS OF THE VOLUME OF INTERNATIONAL MIGRATION
Demographers analyze the determinants of the volume of a migratory stream into two components. The first concerns the specific propensity to migrate for individuals of each given type. The second concerns the number of individuals of each given type. The volume of a migratory stream can be calculated as the sum of the products obtained by multiplying the specific propensity to migrate for individuals of each given type by the number of individuals of that type.
The determinants of the propensity to migrate may conveniently be analyzed in terms of a preference system, a price system, and the total amount of resources available for all goals (Heer 1975, 1996). The preference system describes the relative attractiveness of various places as goals for potential migrants, compared to other goals that their resources would allow them to pursue. An area's attractiveness is the balance between the positive and negative values it offers.
Among the most important of the positive values is the prospect of a better-paying job. Other positive values achieved by migration include the chance to live in a more favorable climate, freedom from persecution, opportunity for marriage, and continuation of marital ties. In the case of forced migration, the positive value achieved is simply to save one's own life.
However, international 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 the disruption of such relationships (Massey et al. 1987). Other negative values created by international migration are the necessity of learning new customs and, often, a new language. Laws restraining legal entry or departure are also, of course, very important deterrents to international migration and will be discussed later in more detail.
The price system describes the costs in money, energy, and time, which cannot be used in the pursuit of other goals, imposed by a given migration decision. Since the cost of international migration generally varies in direct proportion to the distance traveled, the number of immigrants to a given place tends to vary inversely with the distance.
The total resources available for all goals also affects the decision to migrate. If the only draw back to migration is the expense of the move, an increase in monetary income should increase the probability of migration.
MAJOR STREAMS OF INTERNATIONAL MIGRATION
Certain major streams of international migration deserve mention, either because they have had important historical consequences or because they otherwise exemplify unusual patterns. One of the earliest streams of international migration with historical significance was the westward movement of nomadic tribes in Europe and Central Asia at the time of the fall of the Roman Empire. The many tribes that moved westward during this period included those speaking Celtic, Germanic, and Ural-Altaic languages. As the easternmost tribes moved westward, they pushed forward the tribes in front of them. One suggested explanation for this extensive migration is that the grasslands of Central Asia had become desiccated. A second possibility is that an expanding Chinese Empire disrupted the life of the nomadic tribes near its borders and, thus, provoked the movement of all the other tribes (Bury 1928; Huntington 1924; Teggart 1939).
The European and African migrations to North America, South America, and Oceania have probably had more important historical consequences than any other migratory stream. This flow began slowly after Columbus's voyage to America in 1492. It has been estimated that more than 60 million Europeans have left for overseas points in the centuries since then. However, net migration was lower, since many of those leaving Europe later returned (United Nations 1953, pp. 98–102). The migration from Africa to the New World was almost wholly a forced migration of slaves. The first slaves were brought to the colony of Virginia in 1619, and the slave trade in the United States was not legally ended until 1808. During the period of slave trade, about 400,000 Africans were brought to the United States (U.S. Bureau of the Census 1909). The impact of the migration of slaves is revealed by the fact that, in 1790, 20 percent of the 4 million persons in the United States were black.
During the twentieth century, the origin of immigrants to the United States shifted drastically away from Europe and toward Asia and the Americas. This change is illustrated in Figure 1, which shows the number and percentage distribution by region of last residence of immigrants to the United States by decade from 1891–1900 to 1991–96.
The emigration from Puerto Rico to the mainland United States, of major magnitude in the years following World War II, is of interest because it exemplifies an extremely high rate. According to the 1970 census, the combined total of the population of Puerto Rico and of persons in the United States of Puerto Rican birth or parentage was about 4.1 million, of which around 1.4 million were in the United States. Thus 33.9 percent of all Puerto Ricans were on the mainland (U.S. Bureau of the Census 1971, 1973).
Immigration into Israel following World War II is likewise noteworthy because it exemplifies an extremely high rate. In 1948, when independence was established, the total population of Israel was 650,000; by 1961, after the influx of more than 1 million immigrants, it had risen to 2.2 million (Bouscaren 1963; United Nations 1966).
Perhaps the world's largest gross interchange in a short time took place in India and Pakistan following the 1947 partition of British India and the establishment of these two areas as independent states. This migration is also of interest because it was impelled rather than free. In the face of violence, Hindus and Sikhs in Pakistan moved to India and Muslims in India moved to Pakistan. From 1947 through 1950, 10 million persons migrated from Pakistan to India and 7.5 million from India to Pakistan (Spate 1957).
The two most recent major streams of international migration exemplify what has been termed labor migration. Labor migration is said to occur when immigrants are legally admitted to a nation for defined time periods in order to alleviate a shortage of labor. Labor migrants are not given the right of permanent residence. The first stream was the large-scale migration of workers into the prosperous nations of northern and western Europe from poorer nations in the Mediterranean region such as Italy, Spain, Portugal, Yugoslavia, Greece, Turkey, Algeria, and Morocco (Massey et al. 1998). This stream began around 1960 and ended in 1973, following the sudden elevation of petroleum prices by the Organization of Petroleum Exporting Countries (OPEC). The proportion of the total population that was foreign increased substantially in all of the northwest European nations. For example, from 1960 to 1970, the foreign population of the German Federal Republic increased from 1 percent to 5 percent and that of Switzerland from 9 percent to 16 percent (Van de Kaa 1987). The second major stream was the large-scale migration of workers into the major oilproducing nations in the Persian Gulf region out of such nations as Jordan, Egypt, Yemen, Pakistan, and India (Massey et al. 1998). For example, from 1957 through 1975, 70 percent to 75 percent of the total labor force in Kuwait consisted of foreigners (Birks and Sinclair 1981).
CONSEQUENCES OF INTERNATIONAL MIGRATION
One may examine the possible consequences of international migration for the individual, the area of net emigration, the area of net immigration, and the larger social system, which includes areas of net emigration and net immigration. The discussion must be in part speculative, since knowledge about these topics is incomplete.
Before a move, an immigrant will have anticipated a net balance of favorable consequences. Sometimes, however, reality will fall short of expectations, and dissatisfaction will provoke the immigrant to either return to the nation of origin or, on occasion, to move on to some other nation.
Net emigration may have several important consequences for an area. By relieving population pressure, it may cause the average level of wage and salary income to rise. Remittances from emigrants may also be helpful. On the other hand, net emigration may cause the value of land and real estate to decline. Moreover, areas of net emigration suffer the loss of investments made to raise and educate children who spend their productive years elsewhere. This loss is particularly large when the individual receives a higher education prior to emigration. Such a loss is termed brain drain. Finally, since emigration rates are selective by age, nations with substantial net emigration may have relatively few young adults relative to the number of children and the aged.
Net immigration may also have important consequences. If the area is definitely underpopulated, the resultant population increase may help the nation to achieve economies of scale (reduction in the cost of goods obtainable by increasing the scale of production and marketing) and, thus, raise the general standard of living. Under other circumstances, net immigration may result in some decline in average wage and salary income. In either case, a net flow of immigrants tends to raise the price of land and real estate. Furthermore, in general, net immigration increases the proportion of young adults in the total population. Dependent on their composition, immigrants may receive either more or less in government benefits than the amount of their tax payments. Finally, net immigration may make the population more heterogeneous with respect to race, religion, or language.
For the system compromising the nations of both net inflow and net outflow, the direct effect of international migration is of course to promote a redistribution of population. If migrants have been responsive to differences in job opportunities, this redistribution may further the economic development of the total system. Moreover, a substantial amount of international migration responsive to job opportunities might also induce a decline in the degree to which there is economic inequality among nations. Unrestricted international migration might make the poor nations richer and the rich nations less prosperous. However, there is substantial disagreement among scholars as to what the effect of unrestricted immigration from the poor nations might be on the prosperity of the rich nations such as the United States. Simon (1984) believes that net immigration to the United States will serve to increase its average income. Davis (1981), on the other hand, takes a much more pessimistic view. Additional analysis of the consequences of immigration from poor nations to the United States is found in a study sponsored by the National Research Council (Smith and Edmonston 1997, 1998).
LEGISLATION AFFECTING IMMIGRATION AND EMIGRATION
National laws concerning immigration have varied from almost complete prohibition to positive encouragement. Laws restricting emigration are now relatively rare but have been of important consequence in modern times for at least one nation, the USSR.
In the seventeenth and eighteenth centuries, a mercantilist ideology, which saw a large population as the key to national wealth and power, encouraged many of the governments of Europe to attempt to prohibit emigration and to encourage immigration. In the late seventeenth century, the French minister Colbert enacted legislation prescribing the death penalty for persons attempting to emigrate or helping others to emigrate, except to a French colony. In 1721, Prussia passed a similar law. Moreover, the Prussian emperor Frederick the Great invested state funds in subsidizing the settlement of immigrants. In eighteenth-century Russia, both Peter the Great and Catherine the Great subsidized colonists from abroad, mostly from Germany (Glass 1940).
The nineteenth century, influenced by the economic doctrine of laissez faire, was the great period of unrestricted international migration. During this century the European governments freely permitted emigration, and the newly independent United States of America welcomed millions of immigrants.
After World War I, the United States took a more active role in restricting international immigration. The major events in this connection were changes in immigration law in 1921 and 1924 that greatly restricted the number of immigrants to the United States, establishing a quota for each of the countries outside the Western Hemisphere. Furthermore, the nations of northwestern Europe was given much larger quotas relative to their populations than those of southern and eastern Europe. This was done even though, in the immediately preceding years, rates of immigration from southern and eastern Europe had been much higher than those from northwestern Europe. The justification made at the time for the quota differentials was the presumed greater ease with which immigrants from northwestern Europe could assimilate (Eckerson 1966).
By the 1960s, a changing climate of opinion with respect to the inferiority or superiority of different ethnic groups made it possible for President Kennedy to advocate the abolition of the discriminatory national-origins quota system, and a law accomplishing this was enacted in 1965 under the Johnson administration. The 1965 law called for the abolition of the national-origins quota system as of July 1, 1968, but, nevertheless, imposed an overall annual quota of 170,000 immigrants from outside the Western Hemisphere and 120,000 from within it (exclusive of immediate relatives of U.S. citizens). This legislation granted preference to persons with relatives already in the United States, to persons with needed occupational skills, and to refugees. Additional legislation passed in 1976 abandoned the separate quotas for the two hemispheres and imposed a 20,000 limit on immigrants from any nation in the Western Hemisphere (the 20,000 limit had previously been in existence only for Eastern Hemisphere nations). The major effect of the 1976 legislation was to make it more difficult for Mexicans to enter the United States legally.
Some nations, while placing severe restrictions on immigrants in general, have made use of positive inducements to encourage immigration from selected nations or groups. Currently the best example of such legislation is that of Israel, which has committed itself to encouraging the immigration of Jews from anywhere in the world. Formerly, Canada and Australia also exemplified such policies of selective encouragement. Each of these nations subsidized immigrants from European nations while placing severe restrictions on the immigration of nonwhites (Bouscaren 1963; Petersen 1964).
The United States, Australia, Canada, and Israel have laws that allow immigrants permanent residence leading to citizenship. Since 1950, other nations, particulary in northwestern Europe and in the Persian Gulf, have had policies that encourage only labor migration, that is, migration of workers, mostly male, who were supposed to return to their native countries following a fixed term. In the case of the European nations at least, these policies had unintended results. The contract workers were allowed to bring their dependents to live with them. Hence, they became permanent immigrants even though this was not the result intended by original policy (United Nations 1982).
In many nations of the world, particularly in the United Stated, a major phenomenon is the existence of illegal, or undocumented, immigrants. A necessary condition for the existence of illegal immigration is a lack of congruence between the laws regulating the supply of legal immigrant opportunities and the demand for them. For example, the demand to immigrate to the United States from a particular nation should be a reflection of that nation's population size and the average propensity to immigrate to the United States if there were no legal restrictions. Accordingly, nations with large population size are likely to have more immigrant demand than nations with small populations; yet all nations, without regard to population size, have the same annual quota. Furthermore, national differences in individual propensity to immigrate to the United States should be a function of such variables as the difference in standard of living compared with that of the United States, difference in degree of public safety compared to the United States, proximity to the United States, degree of similarity with the language and culture of the United Stated, and prior existence of immigrants that allows for chain migration. According to the official estimate of the U.S. Immigration and Naturalization Service, there were 5 million undocumented immigrants in the United States in October 1996. Of these, 2.7 million, more than half the total, were from Mexico. An additional 335,000 were from El Salvador and 165,000 from Guatemala (U.S. Immigration and Naturalization Service 1997, p. 198). Given Mexico's population size and presumed high average propensity for immigration to the United States, one can easily explain why such a very large proportion of all undocumented persons in the United States have been from that nation (Heer, 1990). An additional fact of interest is the high proportion of undocumented immigrants residing in California. According to the official Immigration and Naturalization Service estimate for October 1996, 40 percent of all undocumented immigrants were living in that state (U.S. Immigration and Naturalization Service 1997).
Rising concern over the extent of undocumented immigration into the United States led the U.S. Congress to enact the Immigration Reform and Control Act of 1986. The intent of the legislation was to eliminate the presence of undocumented aliens in the United States either by legalizing their status or by forcing them to leave the country. This act had two key provisions. The first was the imposition of sanctions upon employers who knowingly employed illegal aliens. The second was the provision of a process whereby undocumented persons who had lived in the United States continuously since January 1, 1982, or had worked in U.S. agriculture for ninety days in the period from May 1985 to May 1986 were allowed to become temporary legal residents. After a short time, they would be allowed to become permanent legal residents. The success of employer sanctions is problematic because sanctions can be applied only if the employer knowingly hires illegal aliens and because it is relatively easy for an undocumented person to present to the potential employer either fake documents or the documents of some other legally resident person. On the other hand, more than 3 million persons applied for legalization of status after the act was passed, among whom about 2.3 million were from Mexico (U.S. Immigration and Naturalization Service 1990).
In 1998 more than 80 percent of the world's 5.9 billion persons lived in one of the less developed nations. The annual rate of natural increase in these nations was around 1.7 percent; in the developed nations it was only 0.1 percent. In the developed nations per capita gross national product was $20,240; in the less developed nations, only $1,230 (Population Reference Bureau 1998). These facts imply a strongly increasing demand for immigration to the developed nations from the less developed. Given the current barriers to legal immigration imposed by the developed nations, undocumented immigration will be of increasing prevalence unless the governments of the developed nations take extraordinary measures to curb it.
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David M. Heer