Fertilität und Wohlbefinden

Auf einen Blick Projekte Publikationen Team


Fertility Change in Urban and Rural Areas of the Developing World

Mathias Lerch, Andres Castro

Ausführliche Beschreibung

Previous research did not reveal patterned regularities in rural-urban fertility gradients over calendar years beyond the universal finding of earlier fertility decline in cities. This limits our ability to understand and project contemporary population change in a world that is mainly urban.

In this project, we analyze trends in urban fertility. We also question whether the inverted U-shaped evolution in the rural-urban fertility differential over time – as implied by theories of the spatial diffusion of behavioral innovations – is confirmed when looking at the issue from a longitudinal perspective. Further, we assess how birth limitation diffuses within urban populations, from urban to rural areas, and we investigate the role migrants play in explaining the fertility level and the trajectory of decline in cities. We look at 60 countries, spanning Africa, Asia, and Latin America.

The project builds on more than 140 repeated and country-specific World Fertility Surveys and Demographic and Health Surveys. A subproject focuses on the fertility of birth cohorts, distinguishing migrant from non-migrant women to eliminate the perturbating effect of changing intensities in migration flows on the assessment of the place-specific diffusion of fertility change. To control for international differences in the demographic and urbanization contexts, we analyze fertility trends over the course of the national fertility transitions and estimate average within-country trends in urban and rural fertility by continent, using time-series regression models with country fixed effects. Total cohort fertility is estimated via cohort parity progression ratios, i.e., the probability that women who already gave birth to a number of children will have another child. The quality of these estimates is assessed by cross-validating the results from successive surveys for overlapping cohorts. In another subproject, we analyze fertility over calendar years and focus on the complex structural and behavioral influences of in-migrants on urban fertility trends.

Our results reveal impressive similarities in the pace of urban fertility decline across the three continents. This implies that we can confidently predict long-term fertility trends in urban areas and that more disaggregated methodologies of urban population projections should be developed. Another key conclusion is that the hypothesized inverted U-shaped evolution in the rural-urban differential over cohorts was confirmed only for Latin American countries. In Asia, the level of rural excess fertility was less pronounced and did not decline among the latest cohorts observed. In Africa, the rural-urban fertility differential increased monotonically over cohorts to the highest levels observed. The international diversity in the national trajectories of fertility decline is therefore predominantly driven by the pace of the urban-to-rural diffusion of fertility decline.



Schlagworte (Region):

Afrika, Amerika, Asien


Lerch, M.:
MPIDR Working Paper WP-2020-014. (2020)    
Lerch, M.:
Population and Development Review 45:2, 301–320. (2019)    
Lerch, M.:
PLoS One 14:7, e0219624–e0219624. (2019)    
Lerch, M.:
MPIDR Working Paper WP-2017-011. (2017)    
Das Max-Planck-Institut für demografische Forschung (MPIDR) in Rostock ist eines der international führenden Zentren für Bevölkerungswissenschaft. Es gehört zur Max-Planck-Gesellschaft, einer der weltweit renommiertesten Forschungsgemeinschaften.