Much shouting over in the US about how covid has reduced US life expectancy. Complete and utter nonsense of course. What has been reduced – and ain’t this a shock for a pandemic – is current lifespans. That doesn’t change expected lifespans in the slightest.
The problem is that people are forgetting what is being measured:
Life expectancy in the United States dropped a staggering one year during the first half of 2020 as the coronavirus pandemic caused its first wave of deaths, health officials are reporting.
Minorities suffered the biggest impact, with Black Americans losing nearly three years and Hispanics, nearly two years, according to preliminary estimates Thursday from the Centers for Disease Control and Prevention.
No, that’s just not right.
Life expectancy is how long a baby born today can expect to live, on average.
The problem is that that’s what we all think it is but that isn’t in fact what is measured.
Instead, we measure the age at death of the current generation of people dying. Well, obviously, because we don;t know the age at which people just born are going to die.
The age at death of people now is a proxy for the age at which young people will die. But like all proxies we’ve got to grasp that it is indeed a proxy.
So, do we think that 80 year olds dying now of Covid affects the likely lifespan of a baby born this year? No, actually, we don’t. Therefore while the current average age of death has declined we do not think that expected lifespan has changed in the slightest.
This is also rather more than just a Parp! at journalists. Failing to understand what is a proxy measurement and what a direct observation is the cause of many an error. It’s something to guard against therefore.