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The Actuary The magazine of the Institute & Faculty of Actuaries

Mortality mistakes too common, says Institute and Faculty

The Institute and Faculty of Actuaries' Longevity Bulletin argues that period life expectancy, commonly quoted as the average number of additional years a person can be expected to live for, is not realistic as it assumes mortality rates are frozen to that time period.

Alison O'Connell, editor of the Bulletin, said: "Period life expectancy does not take into account likely future mortality changes, needed to produce a realistic picture of future lifespans.

"Instead, cohort life expectancy, increasingly used by actuaries, demographers and policy makers, does make an allowance for how mortality is expected to change in future."

She added: "A period life expectancy at birth for women of 82 years gives us a summary of average mortality for the UK at the current time to be compared with that for men of 78 years, for example.

"More useful to answer the question "How long can we be expected to live?" is cohort life expectancy. This is regularly updated with projections of what future mortality levels might be. This tells us that women born now are estimated to live on average for over 92 years, and men for nearly 90 years.

"I have collected many examples of mistaken commentary using period life expectancy figures as if they forecast future lifespans. But to use them this way means we underestimate lifespans, and underestimate how fast lifespans have been improving in recent decades."