International migration, which includes both voluntary migration for economic or other reasons as well as the involuntary movement of refugees, is on the rise. Data are uncertain and trends are difficult to track, but, according to the U.N., at least 120 million people (excluding refugees) lived or worked outside of their own country in 1990, an increase from about 75 million in 1965. The annual growth rate of immigration has been steepest in developing countries, and approximately half of all international migration takes place within the developing world. Nevertheless, foreign-born residents accounted for only 1.6 percent of the total population of developing countries in 1990 but 4.5 percent of the population of developed countries. Today, for instance, population growth in member countries of the Organisation for Economic Co-Operation and Development (OECD) is being driven not by natural rates of increase but largely by immigration  . Between 1990 and 1995, 45 percent of overall population growth in developed countries was due to immigration; in Europe, the proportion was 88 percent . (See People on the move.)
|People on the move|
|Annual net intenrational migration totals and migration rates in the world’s major areas, 1990-95|
|Source: United Nations (U.N.) Population Division, International Migration Policies 1995 (U.N., New York, 1996).|
Considering involuntary movements, the number of refugees worldwide doubled between 1984 and 1991, although it has since fallen from a high of about 18 million in 1993 to just about 14 million in 1996, partly as a result of resettlement programs . However, the number of refugees is overshadowed by the increase in the number of internally displaced persons – those who have been forced to flee their homes by armed conflict, persecution, or natural or manmade disasters, but who remain within their national borders. Because of the rising number of civil wars and local conflicts, the number of internally displaced persons now totals an estimated 30 million worldwide, mostly concentrated in some 35 countries. Africa is the worst-affected region, with up to 16 million people having been internally displaced  . Sudan, where a civil war is now entering its 15th year, has the highest number of displaced people in the world, estimated at from 3.5 million to 4 million. Fighting between rival rebel armies, as well as between rebels and the government in the northern part of the country, has destroyed local grain stores and forced people from their grazing and fishing grounds .
Environmental degradation and resource scarcity can help to trigger mass migration. Population growth, land scarcity, and a cycle of droughts and floods has encouraged the illegal immigration of more than 10 million Bengalis