Ezra Klein has an interview today with political scientist Jennifer Sciubba who studies demography around the world. She's the author of a book titled "8 Billion and Counting." But as the conversation quickly points out, we're probably only going to be counting upward for a few more decades. Many of the world's most populous countries already have birthrates below replacement level and the global population will likely peak around 2070 and start to decline after that. 

There are two very different views about all of this. On the left, many environmentalists are eager to see those numbers decline to take the load off the world ecosystem. On the other hand, there are many on the right currently warning about the population decline as a problem for advanced countries like the US.

So, if we look at global population last century, we saw exponential growth, from 1.6 billion at the start of that century to 6.1 billion by the end. Women have, on average, worldwide, about 2.2 children these days. Basically, that is replacement level because that point number, the 0.2 in this case, accounts for children who might not make it to reproductive age. So it’s, in very crude terms, a margin of error. So we’re basically globally at this number.

But in this century so far, we are in a global demographic divide. This is a century about differential growth at this moment. So, we have very low fertility rates in some places, while it’s still high in others. For example, the area in the world where it really is the highest is in parts of sub-Saharan Africa, a handful of countries where it’s still pretty high, over five children per woman on average.

So, there’s a divide, but we’re all moving kind of in the same direction. So when we think about going forward into the second part of the century, that’s really where we’re all going to start converging down at those lower levels. But I could tell you that, and a listener will have a reaction in one direction or the other. I talked to a lot of folks from an environmental standpoint, and they say, thank goodness. Let’s push it lower.

And then, of course, we know those factions in the U.S. — Elon Musk, for example, sees the number and says, that is too low. It needs to be higher. So, it’s a great caveat for us to set out at the beginning that we might be talking about all kinds of numbers and places, but perception and feelings about those numbers, they go hand in hand with this.

Klein seems interested in discussing why this is happening at all. I don't think that's much of a mystery. Birthrates tend to decline as education and wealth go up. This only seems counterintuitive if you've never met a Ph.D. student or a wealthy person. If you have met these people then you already know they are frequently thinking about other things besides having kids (or having more kids). What's more interesting is some of the social reasons why these divides exist.

Yeah. So, for the total fertility rate for the U.S., writ large, is about 1.6 to 1.7 children per woman. So, it’s decently below replacement level there. For the more education you get, typically, the lower it is. It’s this success sequence that we talk about. OK, you’re going to raise your kids to say you’re going to get lots of education. Then you’re going to get a great job. You’re going to buy a home. You’re going to start a retirement account and get some savings and then have children. So, any little blip along that would then push that off more and more.

Something you mentioned that I think is very important is this idea that maybe within this larger individualistic culture and within this larger idea of a success sequence, there are pockets. So, last time I went on a first date, I was 19 years old. That’s because I met my husband then. I was engaged. I thought about this the other day. This sounds crazy, but at 21, on Valentine’s Day, I was 21 years old, and I was engaged. I’ve now been married over 20 years...

That probably sounds absolutely nuts to a lot of your listeners. But you know what? I was the last one of my friends to get married. We were college-educated women. Getting married early looked very normal in my group. In other parts of the country — I mean, I’m from the South, I’m sure you can hear — it is pretty normal to get married. And then you think about my neighborhood — got lots of folks with more than two children. So, what you’re surrounded by and how you kind of measure normal behavior, acceptable behavior, those cultural values and norms, they affect your decisions around dating, marriage, and having children.

I don't know how old Jennifer Sciubba is but her experience sounds a lot like the one I experienced coming out of college. I had lots of friends who got married soon after graduation and that was considered pretty normal circa 1990. Decades later my own kids are around that age and getting married is much less common with one notable exception. And this gets discussed later in the interview. Religious people are still more likely to get married and more likely to have kids than secular people.

It gets hard for me with religion when I try to parse out these different things because there’s a lot going on with, how do you think about the future, or how do you think about the afterlife? How do you think about the purpose of why we’re here on Earth? And religious teachings do come into play there.

So, when we kind of contrast that with a lot of folks I talk to in the environmental movement, they say, we shouldn’t have humans at all because it’s bad for the planet. I mean, these are extremists, but they’re in my email inbox. And so, that’s two really different worldviews about the value of children, the value of people, the purpose of it all.

And that bring me to what was probably my favorite exchange in the whole interview. This won't be new to many of you but it's significant and something I very much believe is true: People have kids when they have faith in the future.

if you told me that a country had a fertility rate hovering around one child per woman, to some degree, I think that also reflects that there are some things in that society that are broken, that people, women particularly, although I always do hate to put it on the shoulders of women, but in those low fertility societies, it seems to be the case that women are not willing to reproduce the current social structures. They are not working for them to a huge degree, to the point that they are willing to opt out of this idea of marriage and having children, and seek a different path for themselves.

So, while low fertility, generally speaking, I think is a positive example, super low fertility is something we need to understand much more to say, does it reflect that people are not optimistic about the future? I mean, having kids is the ultimate faith that the future will be good. And we saw it go low around this time the Soviet Union collapses in Eastern Europe. People feel dismal about the future, and they don’t want to have children.

It fits within my own worldview that people who have some optimism for the future tend to be more conservative and more religious while the people who lack faith often, well...lack faith. Not just religious faith, but faith in their fellow humans' ability to overcome problem by making social or technological changes. 

The very name progressive seems to suggest a belief in progress but too many progressives these days are depressive doomsayers despite the fact that, in many ways, we're doing better than we ever have. A little more perspective from the left would go a long way.