"Life Expectancy" isn't What You Think it is
Taking a break from internet stuff to clear up a pesky misunderstanding
I know I said this is an “internet” newsletter, but that doesn’t mean we’ll only talk about the internet. Some posts will look at broader ideas that are useful for understanding everything else, especially when we look at how the internet is changing society and culture in low-income regions around the world. So this is one of them.
I just spent three months traveling around SE Asia, and I often heard some variant of this statement from fellow travelers:
“Their life expectancy then was only 40 years — so if he became king at 35, he only had a few years to enjoy it!“
There’s a good chance you might think “life expectancy” means something like this, and I’ll admit that I used to, too. But what if I told you this is ~all an illuuuuuusion~?
When we hear the phrase “life expectancy” spoken at a population level, we should hear it as “average life expectancy” — and realize the word “average” is doing a lot of work. It’s glossing over a lot of variability like any other aggregate statistic does: “average income,” say, or “average housing cost,” or “average report card grade” when you were in school and got all A’s and B’s except for that one f***ing F in trigonometry (and what good did trigonometry ever serve anyway?), and brought home a report card with a frustrating C average, even though you didn’t actually get any C’s.
So “average life expectancy” is doing something similar — except almost all the outliers and variability serve to bring the average down. Way down. Historically very few people lived to 120 years old, but a whole lot died before the age of 1.
It’s estimated, in fact, that the infant mortality rate (the number who die before reaching the age of five) was about one in four across the globe as recently as 1950.
Here’s another table showing just how incredibly high infant mortality (the % of a population dying before the age of 1) and child mortality (the % of a population dying before the age of 5) were for much of human history, from this fascinating paper:
I apologize for the gruesome math, but let’s imagine a society where one third of children die before the age of one (“33% infant mortality”), and another one third die before they’re five (“33% child mortality”). Even if the rest of the population, everyone who makes it past five years old, lives to the age of 80, the “average life expectancy” for the society as a whole will still clock in at under 30. Which is low indeed.
Kids live longer, but us Olds are (almost) as Old as we’ve always been
As infant and child mortality have dropped tremendously over the past century, life expectancy has increased, like so:
How did this happen? It’s not magic, even if this clickbait-y TED Radio Hour episode wants to make us think it could be. Modern sanitation, vaccines, clean water and nutrition have made it much, much more likely that an infant lives to be a kid, and then that kid lives to be an adult — and then poof, there’s way fewer people dying at an early age to bring down the average. In other words, some people have always lived to be 70 or 80 or older — but now many, many more of us are doing so.
I don’t want to downplay the fact that other factors can influence the life expectancy of adults. Covid caused life expectancy to drop across the world, air pollution is causing a drop in life expectancy in South Asia, and gun violence is causing a drop in US life expectancy relative to the rest of the world 😠.
And life expectancy, even for those living into adulthood, has ticked up over the past few centuries. But not to nearly the same extent as that accounted for by decreases in infant and child mortality.
So historically, anytime we see something about the “average person in medieval Europe lived only forty years”, we should remember that this “average person” never really existed. It was a lot of people dying very, very young, and then their parents and grandparents living to be (almost) as old as our parents and grandparents do today.
What about the Rest of the World?
I’ve been focusing on life expectancies through history, but the same principles apply when seeing reports of low life expectancies in some places around the world today.
Hans Rosling talked about this in a fantastic video that went relatively viral online a decade or so back — it’s only four minutes long, and well-worth a quick watch.
Rosling’s argument — well-informed by centuries of data — is that, just as life expectancy has risen over time in wealthy countries because of improved sanitation, healthcare, clean water and good nutrition, the same is occurring in poor countries today, for the very same reasons. According to the World Bank, India’s life expectancy in 1960 was 45, and that number increased by nearly two-thirds by 2019, reaching 71.
By comparison, life expectancy in the US was 71 as recently as 1973 — only fifty years ago. And while Japan had a lower life expectancy than the US until the mid-1960’s, the country pulled ahead and now far surpasses the US in this metric.
If you’re interested in any of this, I strongly recommend reading Factfulness, written by Rosling, his son, and daughter-in-law (cute!). It’s an excellent, easy, and even optimistic read, and I’ll be drawing on some of its principles throughout this newsletter.
Also, it’s worth mentioning here that I’ll be using affiliate links to Bookshop.org where possible — purchases made there will not only send money to local, independent bookstores instead of Amazon, they’ll also help fund this newsletter :)
That’s it for the week! Thanks for sticking around, and see you out in the world 🌍🌏🌎
Song of the Week: Richard Houghten — “Saving a Life”