Here’s an interesting sociological fact. It’s mathematically trivial but is hugely important for how we think about the world.
For a long time, a large proportion of the population have been kids and young families. That’s because, until relatively recently, average lifespans were short: children often did not live to adulthood, and the steady state required a continuing supply of replacement births. Then, in the past century, death rates went down, but people were still in the habit of starting parenthood young and having many kids. There were changes in all sorts of things relating to vital statistics, but the population was still predominantly young. Long-term, though, we should expect children and young families to be a smaller proportion of the population.
The steady-state balance between life expectancy and age distribution is clear enough. For example, if everybody lives to be exactly 80, then in steady state the average age will be 40, only 20% of people will be under the age of 15, etc. This is just an approximation, but it gives the general sense of things.
Nonetheless, given centuries of recent experience, it has just seemed like the natural order of things to have lots of children underfoot, to the extent that when a society is low on babies compared to historical expectations, it feels wrong.
Typically this has been framed in terms of the end of exponential population increase, or as a surfeit of old people relative to the number of working-age people to support them, but a lower proportion of children and young family is part of the story.
To this point, sociologist Philip Cohen recommends a demography article by Ansley Coale from 1964: “How a Population Ages or Grows Younger.” Here’s Cohen:
It makes some key observations that are counterintuitive at first and serve as a great introduction to demographic thinking. Most important (according to him in this 1987 interview) is that reducing mortality in populations with high mortality often leads to a younger population — because more children survive. And then he explains that if we want to survive as a species . . . we are going to have to reduce fertility rates drastically, or else live with very high mortality rates. Fortunately, that’s what we’re doing [reducing fertility rates]. But then he’s also sad that the future will be much older, and less vibrant, than the past.
The point is obvious but often seems to get lost in the details. For example, just today this article appeared in the business section of the New York Times:
China Told Women to Have Babies, but Its Population Shrank Again
Faced with falling births, China’s efforts to stabilize a shrinking population and maintain economic growth are failing. . . .
Chinese women have been shunning marriage and babies at such a rapid pace that China’s population in 2023 shrank for the second straight year, accelerating the government’s sense of crisis over the country’s rapidly aging population and its economic future. . . .
9.02 million babies were born in 2023, down from 9.56 million in 2022 and the seventh year in a row that the number has fallen. Taken together with the number of people who died during the year — 11.1 million — China has more older people than anywhere else in the world . . .
The shrinking and aging population worries Beijing because it is draining China of the working-age people it needs to power the economy. . . .
I like this article a lot more than many articles on the topic, in that it doesn’t just treat the birth rate as some sort of policy knob to be turned; it focuses on women’s choices. I guess that men’s preferences make a difference here too, but I’ll defer to the sociologists and demographers on this one.
One thing that does bother me a bit about this news article is that it’s so focused on a single country. I mean, sure, yeah, I get it: it’s an article about China so they should be talking about China. I just think they should also mention that birth rates are falling around the world. For example, in the above graph it would be good to see the corresponding lines for some other countries.
There’s also this thing where they seem to be attributing the falling birth rates in part to women’s equality and in part to unequal conditions for women. There seems to be some incoherence in the story, in part because they’re explaining a single trend using multiple predictors. Anyway, I’m not trying to slam the news article—I like it!—; I’m just thinking of ways it could be better.
To return to the Cohen’s post . . . He did this cool thing where he downloaded Coale’s article from 2004, entered it into a word processor, and edited it. He created a scholarly remix, and details are at the end of his post. Here’s Cohen:
It’s a good article for teaching, but it was written before he even knew the Baby Boom was ending, and before fertility fell all over the world, and so on. If you don’t know that history it can be confusing to read, and if you do know the history it is still distracting and you want to keep looking things up to see what’s going on today.
So I [Cohen] updated it . . . The trickiest part was the discussion of global growth rates over the last 2000 years. He took the world from 250 million people in year 0 to 3 billion people in 1960. I wanted to go to 8 billion in 2024. . . .
Then the future projections were a little tricky, too. I got it to this:
If, on the other hand, mankind can avoid nuclear war, pandemics, and population decimation because of global climate change, and bring the fruits of modern technology, including prolonged life, to all parts of the world, the human population must become an old one, because only a low birth rate is compatible in the long run with a low death rate, and a low birth rate produces an old population. In fact, if by 2090 the global expectation of life at birth increases to eighty-two – a level achieved by a few dozen countries so far – and the global number of children born per women falls from 2.3 to 1.9, the global population will peak around 10.2 billion. In that scenario, which is the United Nations current projection, the decline in fertility would make the whole world older than the high-income countries today: with 17 per cent under fifteen and 24 per cent over sixty-five (compared with 16 per cent and 19 per cent, respectively, today).
So, yeah, basic stuff. In the short and medium term there’s the possibility of balancing out demographic changes through immigration; in steady state it doesn’t make sense to expect or demand to have a population with a higher proportion of kids and a fewer proportion of oldsters.
Times have changed, and an important step in going forward is to recognize how history has led us to a misleading sense of what should feel normal.