Demography

Life Expectancy Reported Down, with multiple reasons

I’ve seen another release about the US life expectancy dropping a year during 2020 – but this one didn’t credit Covid exclusively.  It pointed out that the US Life expectancy has been dropping for several years due to an increase in drug overdoses and suicides.  Please remember – causality is inferred, not statistically proven.

Covid, with most fatalities occurring among the the oldest, has a hard time reducing the life expectancy by a year. (Social Security has its work on life expectancy, going back to 1940, another table, for life expectancy at specific ages, is available at here)

The article reminded me of the drop in life expectancy that followed the end of the Soviet Union.  That was credited to alcohol overdoses, violent death, and suicides.  The chart shows that it happened there, so it can happen here.  The thing about the calculated life expectancy is that one 21-year-old male death takes 55.91 years from the life expectancy chart, while a 75-year-old male death takes only 11.14 years from the collective pool.

The Soviet figures suggest that a major economic or governmental change can have some immediate changes – though today’s Russians, who made it through the collapse of the Soviet Union were back on track in 2019.  CDC has released data showing excess US deaths in 2020, but they are by state and weekly.  Hopefully they will condense the data – 50 states and 52 weeks make a spreadsheet that takes a lot of effort to get through.  Summing up the data to one nation and one year will make it a lot easier to comprehend,  The data that is currently available is at this link.  It is interesting to look at – and I expect that they will have it compiled at a national level soon.

Community, Demography

Easy Math but Fake News

Yesterday, I read that US Life Expectancy had dropped by a full year due to Covid.  I didn’t really think about it – I had taught about the drop in life expectancy accompanying the Spanish Flu, and had invented hypothetical plagues for student exercises in demography class.  But when I had the full-year drop in life expectancy cited to me a second time, I realized that large numbers keep us from checking the math, even when the data is readily available.  Here’s the basic math for checking the assertion, worked as we would have in the slide rule era.

The US population is just a little under 330 million.  At present there are approximately 400,000 Covid deaths.  Using the Social Security life expectancy tables was a good decision – the data is readily available to check your work . . . but we don’t need complex math to check the claim that US life expectancy will drop 1 year due to covid.  It’s probably worth mentioning that life expectancy is a statistical thing, accurate for a large group but not particularly accurate for an individual.  I’ve known people who lived past 100 and others who died at 14.  At age 12, they had similar chances to live to old age.

To reduce US life expectancy by one year, Covid would have to take away 330 million years of life (remember, there are 330 million people. If each loses one year…)

This is possible, but to make the math easy, lets state the problem in millions to get away from the tyranny of large numbers. .  We’re left with 330 for population, and 0.40 for deaths.  To reduce US life expectancy by one year, we have to have 330 (million years of life) lost by 0.40 (million people).

US PopulationCovid Deaths
330,000,000400,000
330 million.4 million

Checking the math is nothing more than setting up a word problem: How many years of life are lost for each covid victim? Can there be 330 (million) total years of life lost with 0.40 (million) deaths due to covid?

Well, 330 years of life lost divided by .40 is: 825 years lost per covid death. That implies the average Covid death deprives its hypothetical victim of 825 years of life.  Since average life expectancy is now about 80 years, it looks like several orders of magnitude were lost in someone’s calculations.  The old slide rule techniques still have value in checking one’s work.

The same day, another stats guy ran numbers showing that the average Covid death was 13 years early.  That seems to have a bit more face validity – we can go to the charts that show death rates by age, develop percentages, and check his data against the tables – but I’m still making the math easy:

400,000 Covid deaths X 13 years = 5,200,000 lost years of life, or 5.2 million
5.2 million (lost years) divided by 330 million (population) = 0.0158 years of life expectancy per individual. 
0.0158 X 365 (days in a year) = 6 day drop in life expectancy.

The availability of data makes it possible for demography to be a science for everyone, and not confined to university campuses.