In Brazil, many housing projects allow residents to take in only members of their nuclear household. This rule prevents residents from fulfilling their social obligations, thereby weakening social networks and safety nets. Policies must not create additional burdens for the poor by assuming that low- income people live their lives only in one location. Rural development initiatives need to take into account nonagricultural activities and encourage and support them. At the same time, urban policies must be flexible about housing needs and recognize the importance of rural social networks and social relations even in urban dwellers' lives.
Internal migration is another key facet of rural-urban interdependence.
It cannot be measured easily, however, partly because censuses do not register short-term movements. Anecdotal evidence on return migration links it to worker retrenchments in the formal sector, especially during the implementation of structural adjustment programs in the 1980s. These different kinds of migratory patterns point to the varied influence of regional and national economies. For instance, the relocation of Mexican industries to secondary cities because of government incentives has precipitated the movement of skilled, middle-class workers out of Mexico City. Economic imbalance between locations is not the only cause of migration.