The method known as Network Scale-Up (NSU) - used for expanding social networks - is used to estimate hard-to-count populations, based on the idea that human populations are organized in a complex web of social interactions, to which all individuals, regardless of specific personal attributes, are connected. If we know the pattern of personal networks associated with certain individual attributes, we can estimate "parcels" of the population that have these same attributes. International migrants, especially those who are undocumented, fit into this type of subpopulation whose size is unknown because of the difficulty or even impossibility of measuring it directly. This article aims at describing the Network Scale-Up method and the methodological procedures necessary to estimate the number of international and returned migrants in a hypothetical, medium-sized, Brazilian city.
Network scale-up method (NSU); Hard-to-count populations; International migration
