Work out life expectancy at birth instantly with clear inputs, formula shown and shareable results.
Applies the life table identity linking life expectancy at birth to infant mortality and life expectancy at age one.
Life table identity
e0 = q0 x a0 + (1 - q0) x (1 + e1), where q0 is infant mortality, a0 the average years lived by infants who die and e1 life expectancy at age one
An infant death removes a full lifetime from the average, which is why historical gains came largely from child survival.
Period expectancy, since it applies current mortality rates rather than projecting future improvement.