The CDC recently made waves with a report claiming that COVID-19 reduced American life expectancy by a year in the first half of 2020. But as Peter B. Bach explains over at Stat, that doesn’t mean what you probably think.
“Life expectancy” as it’s typically calculated — in more technical terms, “period” life expectancy — is a weird statistic. It’s an estimate of what would happen if someone lived his entire life in a single period of time, starting it over Groundhog Day–style repeatedly until he died. If you calculate the life expectancy of Americans in, say, 2017, you’re asking how long someone would typically live given the death rates for infants, one-year-olds, two-year-olds, and so on, all within 2017. (An alternative is “cohort” life expectancy, where you track people born in a certain year to see how long they lived.)
Obviously this can be misleading when the time period in question is the first half of 2020, because the result tells you what would happen if someone lived his entire life in a time overtaken by a global pandemic.
Bach provides a calculation that’s a little more helpful:
Analysts estimate that, on average, a death from Covid-19 robs its victim of around 12 years of life. Approximately 400,000 Americans died [of] Covid-19 in 2020, meaning about 4.8 million years of life collectively vanished. Spread that ghastly number across the U.S. population of 330 million and it comes out to 0.014 years of life lost per person. That’s 5.3 days. There were other excess deaths in 2020, so maybe the answer is seven days lost per person.
Hat tip to Eugene Volokh.