The rise in life expectancy at birth

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The roughly two-fold increase in life expectancy at birth over roughly two centuries — from an estimated global average near thirty years around 1800 to about seventy-three before the COVID-19 pandemic. The phrase misleads almost everyone who reads it. Life expectancy at birth is an arithmetic mean over a whole synthetic cohort, so it is dominated by deaths at the youngest ages: a population in which a quarter of children die before their fifth birthday has a low life expectancy even if the adults who survive childhood commonly reach sixty or seventy. What changed was overwhelmingly the number of people dying young, not the age at which old people die. In England and Wales period life expectancy at birth was roughly forty-one years in the 1840s and is around eighty-one today, but life expectancy conditional on already having reached age sixty-five rose by a far smaller number of years over the same interval. The gain was produced by public health, infection control and, later, cardiovascular medicine — not by any intervention in the biology of ageing.