The urban population of the world has doubled since 1950 and is likely to do so again before 2000. Large shifts are occurring throughout the world from agricultural activities in rural areas to non-agricultural activities in urban areas, on a scale and at a rate hitherto unknown

Steps that have been taken to stem the rising tide have been palliatives at best, mainly because they have often been formulated without an adequate knowledge of the causes and consequences of migration. Also, little is known on whether it is possible or desirable to control the flow. The issue is riddled with unanswered questions and, above all, with persistent myths that obscure the search for solutions

Most of the growth in the world's population is taking place in developing countries and most of the projected increase of 1 000 million people between 1999 and around 2010 is likely to be absorbed by cities in these countries - cities already faced with enormous backlogs in housing and infrastructure development, and struggling with increasingly overcrowded transportation systems, insufficient water supplies, deteriorating sanitation and environmental pollution. In spite of this, people continue to migrate to cities in the hope of a better life, often as a result of the devastation of rural economies by land degradation

In 1993, 60 million of China's rural workers were moving, mostly from poor central regions to the coastal cities in search of jobs. It is the first large internal migration of the communist era. For decades, residency controls prevented peasants from moving, creating a pool of surplus rural labourers that had grown to 100 million strong

Major cities in Africa are experiencing rapid growth. Nairobi, Dar es Salaam, Lagos and Kinshasa grew sevenfold during 1950-80, mainly because of rural-urban migration (Johns Hopkins 1998). During 1950-95 the population of Cairo quadrupled from 2.4 million to 9.7 million. Lagos in Nigeria is now even bigger with 10.3 million inhabitants (United Nations Population Division 1997). In 1997, the largest cities in 24 African countries had populations of more than one million each (UNDP 1997), nearly half of them in Western and Central Africa. Rapid urbanization is expected to continue for decades

1. Fears have been expressed that migration is a major cause of rising urban unemployment, overcrowded housing, and relative shortage of public amenities. Migrants unable to find adequate employment or any work at all are forced to live in squatter settlements or inner-city slums lacking even the most basic facilities. The resulting pressure on residential land and housing causes speculation and excessive rents, and generally tends to depress living standards in the urban areas. Similarly migration to the cities affects rural areas; not only does it tend to draw away their more dynamic members, but it may also divert national investment resources towards the towns

2. Globalization policies lead to a number of negative outcomes, including massive population shifts from rural to urban areas, with commensurate poverty, famine, ethnic friction, and degradation of living and working conditions and human rights

1. In the cities, the influx of migrants not only increases the labour supply but also generates new employment by stimulating industrial expansion and other economic activities. In rural areas, out-migration may lead to a reduction of the labour/land radio and provide a new environment conducive to changing rural production techniques. There may be a rising demand from the cities for rural output that stimulates agriculture and rural industrialization, thus helping to raise incomes of country dwellers. Similarly, remittances sent home by migrants may improve the distribution of income between the rural and urban population. Analysis of urban data suggests that migrants attain economic status comparable to that of urban natives in a remarkably brief period of time. There is no evidence that migrants are confined to marginal employment in the cities, or contribute disproportionately to urban underemployment

2. Migration from countryside to city does not in itself create difficulties, since it is part of the process of economic development and diversification. The issue is not so much the overall rural-urban shift, but rather the distribution of urban growth between large metropolitan cities and smaller urban settlements