The Components of Change in Population Growth Rates.

The demographic balance equation relates the population growth rate with crude rates of fertility, mortality, and net migration. All these rates refer to changes occurring between two time points, say, t and t + h. However, this fundamental balance equation overlooks the contribution of historical fertility, mortality, and migration in explaining these population counts. Because of this, the balance equation only partially explains a change in growth rate between time t and t + h as it does not include the contribution of historical population trends in shaping the population at time t. The overall population growth rate can also be expressed as the weighted average of age-specific growth rates. In this article, we develop a method to decompose the historical drivers of current population growth by recursively employing the variable-r method on the population's average age-specific growth rates. We illustrate our method by identifying the unique contributions of survival progress, migration change, and fertility decline for current population growth in Denmark, England and Wales, France, and the United States. Our results show that survival progress is mainly having an effect on population growth at older ages, although accounting for indirect historical effects illuminates additional contributions at younger ages. Migration is particularly important in Denmark and England and Wales. Finally, we find that across all populations studied, historical fertility decline plays the largest role in shaping recent reductions in population growth rates.

Efectos de la migración sobre el crecimiento poblacional a largo plazo de las provincias cubanas / Efeitos da migração sobre o crescimento populacional de longo prazo das províncias cubanas / Effects of migration on long-term population growth in the provinces of Cuba

Cuba es un país que, además de presentar niveles de fecundidad inferiores al nivel de reemplazo, ha registrado un significativo saldo migratorio negativo. Se observa también un intenso flujo migratorio interno cuyo patrón es muy diferente entre las provincias. Debido a la magnitud de estos flujos migratorios, la migración se presenta como un componente demográfico importante en la dinámica poblacional cubana. De esta forma, el objetivo de este trabajo es estimar el efecto de la migración interna e internacional sobre el potencial de crecimiento a largo plazo de Cuba y de sus provincias. Para esto, calculamos medidas de reproducción y de crecimiento poblacional a partir de los métodos demográficos convencionales y de la metodología propuesta por Preston y Wang (2007), que se basa en los métodos de variable r. Considerando el patrón demográfico corriente, en la mayoría de los territorios de Cuba se observa una reducción substantiva en la capacidad de reposición de las generaciones y en tamaño futuro de la población cuando se consideran los efectos de la migración.

Cuba é um país que, além de apresentar níveis de fecundidade inferiores ao nível de reposição, tem registrado um saldo migratório líquido negativo significativo. Observa-se também um intenso fluxo migratório interno, cujo padrão é bastante diferente nas diversas províncias do país. Devido à magnitude destes fluxos migratórios, a migração apresenta-se como um componente demográfico importante na dinâmica populacional cubana. Assim, o objetivo deste trabalho é estimar o efeito das migrações interna e internacional sobre o potencial de crescimento de longo prazo de Cuba e de suas províncias. Para tanto, foram calculadas medidas de reprodução e de crescimento populacional a partir dos métodos demográficos convencionais e da metodologia proposta por Preston e Wang (2007), que se baseia nos métodos da variável-r. Levando em conta o padrão demográfico atual, observa-se, na maioria dos territórios de Cuba, uma redução substantiva na capacidade de reposição das gerações e no tamanho futuro da população quando se consideram os efeitos da migração.

Cuba has shown very low fertility levels, even below replacement level, in addition to significant negative net migration flows. In the country's interior there is intense population mobility, characterized by different migration patterns from one province to another. In this article the effects of both internal and international migration flows on long-term population growth in Cuba and in its provinces are discussed. We estimate reproduction and population growth measures using conventional demographic methods, together with the methodology developed by Preston and Wang (2007), based on variable-r methods. Given current demographic patterns in the majority of Cuban provinces, and when migration effects are accounted for, our analysis shows significant negative consequences for the future maintenance of the Cuban population.