Even in the more developed countries, housing stocks contain large numbers of dwellings that are unfit and even not repairable. In the developing countries, corresponding to the distribution of incomes, a certain duality has come to characterize the major urban areas: the city proper is often barely distinguishable from its counterparts in the high-income countries, while alongside it and linked to it in the economic nexus are the barricados, bustees, bidonvilles, favelas and shanty towns that house what has become known as the marginal or transitional population.