Their studies took them to rural areas of several African and Asian countries to probe the part migration plays in helping rural people maintain and improve livelihoods. It urges policymakers to remove counter-productive impediments to such migration whilst guarding against potential drawbacks. Orthodox economic theories highlight the advantages of a free flow of labour. Yet the research literature repeatedly underlines negative aspects of economic migration. It is often seen as the last resort of impoverished peasants, whose presence may blight the natural environment in areas they adopt.
Migrants are often, moreover, victims of exploitation and causes of dispute.
In the outlook of many policymakers and scholars there has been a tendency to promote the interests of sedentary over migrant groups. However, migration is generally the rule rather than the exception. Migration originates predominantly in rural areas, and migrants to urban areas tend to maintain close links with their areas of origin. Hence any attempt to understand how livelihoods can be maintained or improved should not be restricted to a narrow geographical region, but should incorporate extended analysis of the areas and activities from which migrants draw an income. Field research in Bangladesh, Ethiopia, and Mali reveals various kinds of migration.