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Learn more about longevity
The ideas behind longevity statistics are not complicated, but they are easy to misread. These guides explain the concepts the rest of the site is built on.
The vocabulary
What the words mean, and how they are confused with each other.
02Lifespan vs life expectancy
One is about an individual life. The other is an average built from death rates. They answer different questions.
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03Healthspan vs lifespan
Living longer and staying healthy longer are measured differently, and the gap between them is a real finding.
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The arithmetic
Where the published figures come from, and how they behave.
04How life expectancy is calculated
Life expectancy is not a prediction of when anyone will die. A life table takes the age-specific death rates observed in one period and turns them into the average further years a group would live. SnapLongevity shows WHO's published values rather than recomputing them.
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05Why life expectancy changes as you get older
Once you reach a given age, the people who died younger are no longer part of the group used to calculate your remaining life expectancy.
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The bigger question
What is established about living longer, and what is not.
Continue exploring
- Years ahead explorerSee published remaining life expectancy and survival probabilities for an age, sex and country.
- Healthspan by countryCompare how long people live with how many of those years are expected to be healthy.
- What affects longevityExplore the evidence behind physical activity, fitness, smoking, sleep, strength and diet.
- Longevity articlesRead original stories built from global longevity data and published research.