Cohort vs. period life expectancy: why birth year matters
The two measures answer different questions. The chart uses cohort life expectancy because its rows compare people born in different years.
6 min readModel 2026 · SSA 2026
Research
Read the model before the number
A small evidence library about the concepts behind the chart. Each article names its sources, model version, and limits.
By Life Days LeftModel 2026 · SSA 20264 launch articles
Library
Four questions, answered carefully
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Life expectancy at age 40 vs. life expectancy at birth
The baseline and the cohort adjustment come from different starting ages. Their roles in the model are deliberately narrow—and not interchangeable.
7 min readModel 2026 · SSA 2026
Income and life expectancy: what the Chetty study supports
The underlying study measured a strong population association. The chart uses one published percentile as a baseline; it does not infer anyone’s income or promise that income causes longevity.
7 min readModel 2026 · SSA 2026
Life expectancy by generation: what the chart can show
Generation labels organize birth years; they do not determine lifespan. The chart’s ranges come from dates and a cohort adjustment, not a claim that every member shares one outcome.
6 min readModel 2026 · SSA 2026
Editorial scope
Narrow by design
This library explains the public model and the research it uses. It does not publish personal longevity advice, diagnose health, or convert population associations into individual recommendations.
Source changes are reflected in visible model versions and updated dates. Material corrections are made in the article body, not hidden behind a fresh timestamp.
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