Shared Lifetime and Years of Shared Life Lost

Amanda Martins de Almeida , Max Planck Institute for Demographic Research

The life courses of individuals intersect with those of their relatives, resulting in shared lifetimes that are shaped by mortality and fertility processes. The demographic transition has fundamentally reshaped family structures by reducing fertility and mortality, altering both the number and types of living relatives. However, the temporal dimension of kinship, that is, the amount of time individuals share with their relatives, remains largely unexplored. The present study introduces two formal demographic indicators to quantify this aspect: Shared Lifetime (SLT) and Years of Shared Life Lost (YSLL). SLT measures the expected amount of time a child and their mother are simultaneously alive, reflecting intergenerational exposure and potential for support. YSLL captures the loss of potential SLT due to the death of the mother or the child. Using age-specific fertility and mortality data from the United Nations World Population Prospects (1950 and 2023), I estimate SLT under stable population assumptions for all countries. The findings indicate a consistent rise in SLT between the years. However, substantial cross-national disparities persist: in 1950, a woman born in Germany could expect to share 42 years with her mother compared with 16 in Kenya; by 2023, both increased, but the gap remained large. These findings indicate that demographic change not only modifies kin availability but also impact the duration of intergenerational interactions. Incorporating temporal measures such as SLT and YSLL into kinship demography provides new insight into the lived experience of family ties and the intergenerational transmission of resources, care, and inequality.

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 Presented in Session P8. Demographic Trends, History, Data and Methods