MIGRATION IS referred to as "any residential movement which occurs between administrative units over a given period of time," according to geographers Paul White and Robert Woods (1980).
Other scholars have defined migration as the change in the center of gravity of an individual's mobility pattern.
The destinations of the mobility flows need not, themselves, change as a result of the change in their center of gravity.
For example, in the local intraurban move, the destinations of journey-to-work, recreation, and shopping may remain the same, while in an interurban move, they are likely to change.
The perception of spatial differentiation of opportunities-the idea that different geographical locations offer different levels of potential well-being to various sections of human population- explains why migration occurs.
It is these perceived differences between places that are important rather than any simple "push and pull" mechanism.
Hence, migration occurs because migrants believe that they will be more satisfied in their needs and desires in the place that they move to rather than the place from which they come.
An importance must be placed on the word believe.
Migration occurs as a result of decisions made by individuals in the light of what they perceive the objective world to be like: it does not matter if the migrant holds an erroneous view-it is that erroneous view that is acted upon rather than the objective real-world situation.
Thus, there may be cases where migration occurs despite the lack of an objective reason for it, and other cases where an objective appraisal of the world, were it possible, might suggest that migration should occur where it is, in fact, absent.
In recent times, international migration is at record levels and is unlikely to slow down in the near future.
The number of long-term international migrants (that is, those residing in foreign counties for more than one year), according to the United Nations Population Division, in 1965 was only 75 million, but that number rose to 84 million by 1975 and 105 million by 1985.
There were an estimated 120 million migrants in 1990, the last year for which the detailed statistics are available.
In the 1990s, migration growth continued with the same pace; hence, in 2000, an estimated 150 million people resided outside their county of birth or nationality.
Even with the numbers of international migrants large and growing, it is important to keep in mind that less than 3 percent of the world's population has been living outside their home countries for a year or longer.
International migrants come from all parts of the world and they go to all parts of the world.
In fact, only a few countries are unaffected by international migration.
Many countries are sources of international flows, while others are net receivers, and still others are transit countries through which migrants pass to reach to receiving countries.
Such countries as MEXICO experience all three capacities, as source, receiving, and transit countries.
The noteworthy fact about migration is that it tends to be within regions; migrants often remain within the same continent.
More than half of international migrants traditionally have moved from one developing country to another.
In recent years, however, migration from poorer to richer countries has increased significantly.
While the traditional immigration countries-the UNITED SATES, CANADA, and AUSTRALIA- continue to see large-scale movements as a result of labor recruitment that began in the 1960s and 1970s, Europe, the oil-rich Persian Gulf states, and the "economic tigers" of East and Southeast Asia are now also major destinations for international migrants.
MIGRATION IN PREINDUSTRIAL SOCIETIES In the history of migration, there is no comprehensive evidence of migration until the 19th century, however, information from census and vital registration provides indirect evidence of the nature of migration.
It was once thought that there was little migration in pre-industrial societies, on the grounds that transportation was slow, costly, and often dangerous, and that institutions such as serfdom-or, in England after the 16th century the laws of settlement-hindered mobility.
There is evidence supporting this view.
In 1841, when four-fifths of Sweden's population lived in rural areas, 92.8 percent of the population was still in the country in which they had been born.
Research on parish registers shows that most women married men from their own or nearby villages; until after 1750, four-fifths of all French women married men from places within a few miles or kilometers of their village.
But it does not follow from this that preindustrial communities were completely isolated and lacked mobility.
Studies of English villages in Tudor and Stuart times suggest a remarkable turnover in inhabitants' names that can only be explained by migration, albeit of short distances.
A study of 10 parishes near York, England, shows that of the inhabitants at the end of 18th century, only 40 percent had ancestors there in 1700.
Before 1000, villages were the basic unit of rural settlement; in the following centuries people moved into the woodland between the primary settlements and established hamlets and isolated farmhouses; by the middle of the 13th century, there was little good farmland left, and there was a movement on to marginal land.
Many of the upland areas of Europe were settled for the first time-in NORWAY, in the French ALPS, and in the Vosges and the PYRENEES.
The long-distance movement was more dramatic between 1050 and 1340; there was a movement of Germans east of the Elbe River into sparsely populated Slav areas; in the 12th and 14th centuries, some 400,000 moved into this area.
In southern Europe, the principal movement was by the Spanish southward into the Muslim-occupied areas of Iberia.
But while these two movements have received much attention from geographers and historians, they were numerically less important than the innumerable short-distance moves that completed the rural settlement of western Europe.
By the beginning of 17th century, the great age of rural-rural migration in the west was ending.
It is difficult to estimate the importance of ruralurban migration in preindustrial Europe; even in the 18th century, the overwhelming majority of Europe's population lived in villages, hamlets, and small market towns, except in the Low Countries and England.
Until the 19th century, rural birth rates generally exceeded urban birth rates, and urban death rates exceeded rural death rates; in most towns, and particularly in large ones, death rates exceeded birth rates.
Thus, it is generally assumed that before the 19th century, towns could grow only by immigration from the countryside.
In 1000, Europe had no more than 100 places that could be called towns, and half of them were in ITALY; by 1300 there were 4,000 or 5,000 such places.
The 12th and 13th centuries were a period of urban growth, standing in marked contrast to the preceding centuries.
By 1300, Venice, Milan, and PARIS probably had 100,000 people each; LONDON 50,000.
More important was the proliferation of small towns.
In the 16th century, there were 500 market towns in England.
The 16th century saw not only a renewed growth of population but also rapid urban growth.
The most striking feature of this period was the emergence of a number of very large cities.
London grew from some 60,000 in 1520 to 250,000 in 1600 and had exceeded 500,000 by the end of the 17th century.
Paris, the largest city in medieval western Europe, grew from 250,000 in 1600 to 500,000 in 1700, while Amsterdam, which had only 31,000 people in 1585, had reached 200,000 by 1650.
Epidemic death rates consistently exceeded birth rates in towns: 30,000 people died in 1580 in Paris from typhus; the plague caused 33,000 deaths in 1603, and 41,000 in 1625.
Most of the migrants came to town from comparatively short distances away.
Rural-urban migration thus played an important role in reducing the rate of increase in the rural areas of preindustrial Europe.
In most parts of Europe, there was little increase in urbanization before the 18th century, but the difference in the rates of natural increase between the town and country-it was negative in the former-ensured that some of the rural surplus was absorbed.
It is likely that the rapid urban growth of this period was partially a function of the "push" from the countryside and not only the "pull" of the towns.
It is true that in the medieval and early modern periods, emigration overseas had no significant impact upon the countries of western Europe, but things drastically changed after the discovery of the Americas when considerable numbers did move.
Some 100,000 Spaniards left for the New World in the 16th century.
From 1620 to 1640 in England, 80,000 people left for IRELAND, the West Indies, and the North American colonies.
By 1700, more than 500,000 people of English extraction were living outside England, compared with just over 5 million in England.
THE ERA OF INDUSTRIALIZATION After 1750, European countries experienced a pronounced increase in their total population size, so that by 1850 the population of most countries doubled, except in the case of Ireland and France, and increased rapidly for the rest of the century.
In England, the century after 1750 saw the beginnings, and indeed the maturity, of industrialization.
But in the rest of Europe, industrialization did not get under way until later, and although there was urban growth, rural population increase was almost as rapid, so by the middle of the 19th century, the portion of population living in the rural areas had declined very little.
As a consequence, the countryside of rural Europe had to absorb a great increase in numbers before industrialization had made any progress.
Thus, many parts of western Europe were suffering from rural overpopulation by the 1830s, and this was apparent in the growth of landlessness, the subdivision of farms, underemployment, and falling real wages.
It was only in England that migration to the towns helped reduce the problems of the countryside before 1850, for it was only in England that industrial growth was rapid enough to absorb the rural surplus.
Many European countries experienced remarkable population growth but without any significant industrialization.
Undoubtedly, there was stress in the rural areas of these countries, and while there was some rural migration, the surplus rural population could not be absorbed in the towns.
At this juncture, fortunately, there was an alternative open to the population: emigration to North America.
Many scholars have tended to emphasize the "pull" of North America as the major reason for the mass European migration of the 19th century, but until the 1870s the "push" element in the rural areas of western Europe must had been at least as important.
In many parts of Europe, emigration was the only solution to rapid population growth.
For example, in Norway the population doubled between 1800 and 1865.
Nearly all this increase had to be absorbed in the rural sector.
Migration was the only viable solution.
The first emigrants left in 1825, but they were few until the 1860s, when a crop failure prompted the first mass migration from Norway in 1868 and 1869.
By then, crossing the Atlantic was much cheaper, and the early emigrants had sent home good news and money.
In SWEDEN, urbanization and industrial growth were more rapid after 1870 than in Norway, and the towns took more of the rural surplus.
Nonetheless, 1,105,000 emigrated between 1840 and 1914, the equivalent of 25 percent of the natural increase of this period.
Irish emigration is often thought of as beginning with the famine, but it was already running at a high rate before 1845.
The Irish population doubled between 1754 and 1821, and in the next 30 years there was acute subdivision of farms, an increase in landlessness, falling real wages, and an ever-increasing dependence on the potato crop.
There was little industrial growth and the country remained overwhelmingly rural.
In the absence of any internal outlet for the excess population, emigration was the only solution, and between 1780 and 1845, around 1,700,000 people left Ireland, one-third to Britain, the rest to North America.
The famine then merely accelerated the trend; between 1845 and 1851 about 1 million left, and in the following decade another million.
Since 1950, there has been movement out of developing countries, but on a very small scale.
Thus, by the 1950s annual migration of Latin Americans into the UNITED STATES exceeded that of Europeans, and there has been a considerable flow of migrants from North Africa but not on a scale sufficient to reduce population pressure at home.
In the 19th century, it was possible for some 40 percent of Norway's natural increase to be removed in 50 years, a total of 750,000.
A movement of a comparable proportion of INDIA's natural increase between 1950 and 1970 would have involved over 70 million, approximately equal to the total number of emigrants from Europe since 1800.
Although international migration may have helped relieve population problems in some West Indian islands, and in the future may have similar localized effects elsewhere, there seems no prospect of overseas migration affording a solution to the population problem of densely populated developing countries.#