Los supuestos de método de las relaciones de supervivencia en la medición de la migración interna

Resumen

Several authors have discussed the assumptions underlying the method used to determine survival relationships applied in the measurement of internal migration, especially when the relationships are based on census data.In order to adequately reflect mortality, authors seem to agree that the calculations require that the population used must be closed, with no confounding effects from international migration.This criteria imposes a constraint on the possibilities of measurement and analysis, as it does not make it possible to estimate internal migration of open populations, but only total migration.In this paper, it is shown that if survival relationships could be determined for an open population, those possibilities would be considerably increased.This extension of the method makes it possible to define three cases: a) A closed population with closed survival relationships; b) An open population with closed survival relationships, and c) An open population with open survival relationships.With respect to each of these three cases, this paper shows the various types of estimation errors which may be encountered where census survival relationships and census data are used, in the calculation of internal migration as both sets are affected by shortcomings in the process of gathering the basic data.In addition, the paper shows the necessary conditions in order to attain accurate measurements with this method.These conditions correspond to the assumptions underlying the method, analyzed here for each of the three cases mentioned earlier.It should be noted that one of the conditions mentioned, replaces another shown invalid some years ago by Price.Thus, it is felt that a more systematic discussion of the assumptions underlying the method is presented.