In contrast to the upper boundary of mortality, the lower boundary has so far
largely been neglected. Based on the three key features location (1), sex-specific
difference (2) and level (3), this paper analyzes past and present trends in the
lower boundary of human mortality. The analysis is based on cohort mortality
data for 38 countries, covering all the cohorts born between 1900 and 1993. Minimum mortality is analyzed using observed as well as smoothed estimates. The
results show that the ages at which minimum mortality is reached have shifted to
lower ages. Although the differences have become almost negligible over time,
males are showing higher levels of minimum mortality than females. The level of
minimum mortality was halved more than five times over the analyzed time horizon. The results also suggest that even after more than one and a half centuries of
mortality improvements, minimum mortality has not yet reached a lowest limit,
and is likely to decrease further in the near future. Trends in the three key features
also raise questions about the importance of evolutionary, social, and biological
determinants for the recent and future development of minimum mortality.