What the study found
The study found that lifespan disparity, a measure of variation in ages at death, can be closely explained by statistical features of age-at-death distributions. In adult populations, the first four standardized moments of these distributions determine about 95% of life disparity values.
Why the authors say this matters
The authors conclude that adding skewness and kurtosis, two measures describing asymmetry and tail shape in a distribution, yields new insights into mortality compression and lifespan variability trends. They also note that these measures help show how mortality patterns have shifted over time.
What the researchers tested
The researchers analyzed data from the Human Mortality Database, using 7,408 life tables from 41 countries covering 1751 to 2019. They examined how standard statistical moments, including variance, skewness, and kurtosis, relate to lifespan disparity and its trends.
What worked and what didn't
Remaining life expectancy contributed the most to lifespan disparity, but its share declined over time as variance, skewness, and kurtosis made up larger shares. The study also reports shifts in skewness toward more symmetric age-at-death distributions in recent trends, and kurtosis patterns suggesting a persistent fraction of deaths at distribution extremes, including a plateau in the number of centenarians.
What to keep in mind
The abstract describes an empirical analysis of a mathematical relationship, so the findings are limited to the datasets and populations included. The available summary does not describe additional limitations beyond the focus on adult populations for the 95% result.
Key points
- Lifespan disparity can be expressed as a linear combination of standard statistical moments of age-at-death distributions.
- From 1751 to 2019, the share of lifespan disparity explained by remaining life expectancy declined.
- Variance, skewness, and kurtosis accounted for larger shares of lifespan disparity over time.
- For adult populations aged 30 and older, about 95% of life disparity values were determined by the first four standardized moments.
- Kurtosis patterns suggested a persistent fraction of deaths at distribution extremes and a plateau in centenarians.
Disclosure
- Research title:
- Mortality patterns increasingly shaped by skewness and kurtosis
- Authors:
- Hiram Beltrán‐Sánchez, Oscar E. Fernandez
- Institutions:
- University of California, Los Angeles, Wellesley College
- Publication date:
- 2026-02-04
- DOI:
- 10.1098/rsos.251307
- OpenAlex record:
- View
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