Life expectancy (concept)

Life expectancy is a statistical measure of the average lifespan of a population.

It differs from maximum life expectancy, known as "potential longevity", in that it varies according to the age at which it is measured. Moreover, the value of life expectancy at birth is highly sensitive to the infant mortality rate.

It is used for living organisms,with human life expectancy and that of plants and animals, but also for objects, instruments or organizations, only when it is possible to attribute an age to them, and thus to know the date of creation, appearance or first use, and to identify an event comparable to death for living organisms (destruction, disappearance, definitive breakdown, etc.).

History of human life expectancy[edit]

Eighteenth-century mortality tables[edit]

Major advances in life expectancy and its estimation were made from the middle of the 18th century, thanks to the mortality tables successively published by Antoine Deparcieux (1746), Théodore Tronchin (1748), Pehr Wilhelm Wargentin (1749), Thomas Simpson (1752), Johann Peter Süssmilch (1761), and Daniel Bernoulli (1763), according to whom vaccination against smallpox increased overall life expectancy by three years.

Stagnation and setbacks at the end of the 20th century[edit]

Since the end of the 20th century, life expectancy has begun to fall or stagnate in some countries (in France in 2012, for example), and for the first time in 250 years (excluding wartime periods); it has stagnated for men and fallen slightly for women. According to INED (by its French acronym) and the harmonized ^[1]^[2] European indicator calculated by Eurostat:^[3] "In 2012, life expectancy did not increase...It stagnated for men (78,4 years) and even fell by 0,2 points for women (84,8 years)", while life expectancy in good health (or "life expectancy without activity limitation") is declining in many countries.^[4]

The respective roles of genes and behavior[edit]

Geneticists are also seeking to understand the extent to which our genes influence our life expectancy. According to a recent study based on a family tree constructed by crowdsourcing for 13 million people, these genes are of little importance compared to environmental and behavioral factors: 16%, compared with around 25% previously thought on the basis of previous studies carried out on twins in Scandinavia (this difference could be explained, according to Kaare Christensen (Director of the Danish Twin Registry in Odense), by Scandinavia's history and peaceful environment, which may have given genetics a more important role than the world average).

Semiology of the term "life expectancy"[edit]

This expression is polysemous and can refer to:

Human (or animal) life expectancy, with no indication of age, is generally life expectancy at age zero (birth, onset of function, etc.). We may also refer to life expectancy after the onset of a serious illness, or after surgery or chemotherapy. In the latter cases, we can also refer to "life expectancy at five years", in other words in the years following the first five years after;^[5]
life expectancy in good health (Eurostat statistics) anddisability-corrected life expectancy (WHO statistics);
the life expectancy of a population of objects subjected to given stresses (shear, thermal, mechanical, etc.).

However, it does not reflect "potential longevity", defined as the maximum lifespan that a living creature of a given species, an object, a machine, etc., is expected to reach.^[6]

In statistics, "expectancy" is a neutral mathematical term (equally applicable to desirable and undesirable events) denoting an average.

Mean or median[edit]

In some cases, "service life", or "mean running time", is calculated as a median rather than a mean.

References[edit]

↑ Robine, Jean-Marie; Jagger, Carol; REVES, Euro (2003). Creating a coherent set of indicators to monitor health across Europe: the Euro-REVES 2 project. European Journal of Public Health. pp. 6–14. Search this book on
↑ Eurostat (2012). A synthesis report on the 2012 consultation on further harmonisation and documentation on the EU-SILC1 PH0302 variable. Eurostat, Unit F-5: Education, health and social protection, Luxembourg. Search this book on
↑ "INSEE : Tableaux de l'économie française - édition 2013" (PDF). Revue "Population et société" (499). 2013.
↑ Kaiser, Jocelyn (2018). Thirteen million degrees of Kevin Bacon: World’s largest family tree shines light on life span, who marries whom. Science. Search this book on
↑ "Cancer du poumon: l'espérance de vie a-t-elle progressé ?". France 5. 2012.
↑ "Informations lexicographiques et étymologiques de 'Longévité'". Trésor de la langue française informatisé. Centre national de ressources textuelles et lexicales.