The interplay between migration and development has for some time been high on the policy agenda of international institutions and national governments in Northern and Southern hemisphere countries. This political context has encouraged the scientific community to brainstorm on the issue and by so doing on the different aspects of the links between migration and development. There are various migratory patterns that present serious difficulties of observation and analysis, and this is because many migratory characteristics are interconnected and become confused in the migratory routes: Seasonal migrations from rural areas to cities can evolve to international migrations. However, a major problem remains that official statistics on migrations are either fragmentary or quite inexistent and generally fail to cover most of the patterns of mobility.