Unequal lifetimes: An example of infant and child survival in the past

In human populations, there is a strong negative association between life expectancy and the level of lifespan inequality (Smiths and Monden 2009; Vaupel et al. 2011). The distribution of lifespans is affected by several variables at different levels of aggregation, which may not have the same impact on all age-groups. Thus, besides individual frailty (Vaupel et al. 1979), access to clean water in the community and breastfeeding practices within the family are decisive for survival at the youngest ages. Some studies (Zaba and David 1996; Edvinsson et al. 2005; Bengtsson and Dribe 2010; Willführ and Gagnon 2012) have shown that in historical as well as in some contemporary populations infant and child deaths are concentrated in a reduced number of families.
This study aims to explore the distribution of infant and child deaths at different levels of aggregation in an historical population, namely France during the 18th and the 19th centuries. The results show that total inequality in the distribution of lifespans has decreased as life expectancy has risen.
In the past, most of the inequalities in the distribution of lifespans were due to mortality in the youngest age-groups. Excess urban mortality was a major source of inequalities in the distribution of lifespans. At the micro-level, infant and child deaths were unequally distributed among women. Heterogeneity between the mothers concerning their infant-care practices was possibly an important source of differentials in infant mortality. Today, most of the inequalities in the distribution of lifespans are due to heterogeneity in the ages at death within the oldest age-groups.