Birth replacement in Spanish regions. Internal and international migration from 1975 to 2005

Luis Alberto Del Rey Poveda, Universitat Autònoma de Barcelona
José Antonio Ortega, United Nations

In this paper we analyze population reproduction in the Spanish regions since 1975 to 2005 using a new indicator, the Birth Replacement Ratio (BRR). Population replacement requires to consider the interaction of mortality, fertility and migration. In contexts of low or very low fertility and mortality, migration becomes a major determinant of demographic dynamics. The traditional indicators for analyzing replacement such as the TFR or the NRR, do not incorporate the effect of migration, hence they are inadequate under those circumstances. The BRR is an indicator that compares the total number of births in the current year to the size of the generation of mothers at Birth: that is, a weighted average of the births of women in the past with the weights corresponding to fertility rates in the present. The BRR incorporates the effect of migration on the evolution of births and gives a precise indication of the reproductive situation of a population at each moment. Furthermore, when information is available regarding the population distribution of women by age and place of birth it is also possible to estimate the contribution of emigration and immigration to birth replacement of the current birth generation. Using this indicator, we observe that both internal and international migration have marked the different reproductive situation in Spanish regions since the seventies. In particular, the unprecedented immigration received in the last decade has contributed very importantly to the increase in the number of births. We characterize the different regions in Spain according to the patterns observed throughout this period. We see that the new current of international migration has substituted the previous internal migration in the case of the receiving regions and has contributed to lessen the reproduction crises in the traditional sending regions.