Top and bottom longevity of nations: a retrospective analysis of the age-at-death distribution across 18 OECD countries

BACKGROUND: Similar to the study of the distribution of income within countries, population-level health disparities can be examined by analyzing the distribution of age at death. METHODS: We sourced period-specific death counts for 18 OECD countries over 1900–2020 from the Human Mortality Database. We studied the evolution of country-year-specific distributions of age at death, with an examination of the lower and upper tails of these distributions. For each country-year, we extracted the 1st, 5th, 10th, 90th, 95th and 99th percentiles of the age-at-death distribution. We then computed the corresponding shares of longevity—the sum of the ages weighted by the age-at-death distribution as a fraction of the sum of the ages weighted by the distribution—for each percentile. For example, for the 10th percentile, this would correspond to how much longevity accrues to the bottom 10% of the age-at-death distribution in a given country-year. RESULTS: We expose a characterization of the age-at-death distribution across populations with a focus on the lower and upper tails of the distribution. Our metrics, specifically the gap measures in age and share across the 10th and 90th percentiles of the distribution, enable a systematic comparison of national performances, which yields information supplementary to the cross-country differences commonly pointed by traditional indicators of life expectancy and coefficient of variation. CONCLUSIONS: Examining the tails of age-at-death distributions can help characterize the comparative situations of the better- and worse-off individuals across nations, similarly to depictions of income distributions in economics.