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Changing Demographic Rates Reshape Kinship Networks

Sha Jiang
Research Group: Kinship Inequalities, March 22, 2023

Sha Jiang from Stanford University used a time-varying kinship model to investigate the changes in kinship networks in response to time-varying demographic rates.


Demographic rates (especially fertility and mortality) are key determinants of kinship networks, and change at different speeds across countries. The number and age of kin jointly determine the intensity/frequency and the type of companionship/support that an individual can get from or provide to their kin. In this study, she uses a time-varying kinship model (Caswell and Song, 2021) to investigate the changes in kinship networks (both numbers and ages of kin) in response to time-varying demographic rates, with a focus on the speed of change.

She highlights here several findings. Firstly, the difference in the number of kin among peers, even within a generation, is much greater under a fast fertility decline than under a slow decline. For example on average, under a fast fertility decline, a 65-year-old individual has about 20% fewer daughters compared to a 70-year-old individual at a certain year, while the difference is only 7% under a slow decline. Secondly, the speed of fertility decline has a dramatic effect on the mean and on the variability of the ages of kin. Thirdly, she show that a cohort perspective is valuable for understanding the changes in the size and age of kin under different fertility levels, as well as the effect of the age pattern of fertility. Finally, she finds that changes in the age pattern of mortality have large effects on the number of kin.


Sha Jiang a final year Ph.D. student in the Tuljapurkar Lab at Stanford University. Her research interests lie broadly in analyzing the impacts and trends of demographic transitions, with an emphasis on the role of uncertainty in demographic rates. Specific topics include mortality inequality and its implications for the Social Security system, the variation in fertility patterns and in lifetime reproductive success, and the variability in the life histories of animals and plants and its effect on population resilience. Changes in human fertility and mortality affect the dynamics of kinship networks and are another important part of her research. In this work, Jiang seeks to shed light on the impact of demographic transition on familial relationships and social structures.

The Max Planck Institute for Demographic Research (MPIDR) in Rostock is one of the leading demographic research centers in the world. It's part of the Max Planck Society, the internationally renowned German research society.