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Kira Bindrim: You don’t have to look far in popular culture to find anxiety about overpopulation. In the movie Elysium, too many people leads the super-wealthy to move to a spaceship. In Logan’s Run, they just kill everyone when they reach 30. One movie even had scientists solve this problem by shrinking people to miniature sizes.

But while Earth’s population is big—around 7.8 billion people—that size is not as threatening as you might think. Population growth actually peaked decades ago, and within this century, that growth could stop entirely. To understand how, you can look at the replacement rate, or the number of children a person must have to effectively replace themselves.

The replacement rate is an interesting tool for anyone trying to understand the future of the planet. But it’s also a reflection of millions of individual decisions, which are impacted by everything from family planning to cultural expectations. And that makes the replacement rate an indicator of the world we’ll live in, and the demographic shifts that stand to reshape it.

This is the Quartz Obsession, a podcast that explores the fascinating backstories behind everyday ideas, and what they tell us about the global economy. I’m your host, Kira Bindrim. Today, the replacement rate: counting our chickens before they hatch.

I’m joined now by Tripti Lahiri, who is Quartz’s Asia editor, currently based in New Delhi. Tripti, I want to start by going right back to the contradiction I talked about a second ago. For me, and I think for a lot of people, there’s this assumption that the global population is just going to keep getting bigger indefinitely and at some point that’s going to become a very real threat to the quality of life for humans. What, if anything, is incorrect about that assumption?

What is the replacement rate, and how is it different from fertility rate?

Tripti Lahiri: So what’s very interesting is that we’re actually living in a moment where some of us are gonna live to see a time when the global population is actually not gonna keep growing. What exactly that number is that a tops out as, we don’t really know yet. There’s a huge range of estimations. One is maybe 11 billion by the end of the century, but it could be less and it could happen earlier. So we are definitely reaching the end of what is called a demographic transition.

Kira Bindrim: So where, historically, clearly from some of my examples, we had this big anxiety around a growing population, now maybe we should be turning our attention to some of the short- and long-term impacts of a shrinking one, or at least a not-rapidly-growing one. I want to get into some terminology. Let’s start with, what is the replacement rate, and how is it different from birth rate or fertility rate?

Tripti Lahiri: So when we talk about fertility rate, we’re usually talking about whatever is the average births per woman in a particular population. So, for example, in China right now, that’s like 1.7. In Israel, it’s three. So that’s, like, reflective of what’s actually happening. And then there’s another concept, which is the replacement rate. And that’s the fertility rate where, in theory, and leaving aside other things like immigration, that if you had that rate of fertility, then, at a certain point, the population would not grow, it would not shrink, but it would just stay the same. And right now, that number is believed to be around two, 2.1, depending on the particular country and conditions.

Kira Bindrim: So what factors impact a country’s replacement rate? By which I mean, why isn’t it always two? You know, two people have two kids, and go on forward?

Tripti Lahiri: Yeah, so there are two things that matter a lot. One of them is sex ratios, and then the other thing is health in that country, and particularly childhood health. So for example, you know, why do we say women should have 2.1 children? The idea is that woman really does need to replace herself—there has to be another girl that grows to be of reproductive age, and then she’ll have a child, and so on and so forth. So because of sex ratios at birth, you know, if you want that woman to have at least one daughter, chances are if she has two kids, one will be a daughter. And the other thing is health—yeah, if you have kids, but they don’t make it to age five, let alone age 15, then you need to have many more kids in order for there to be a daughter at age 15 who will then have children at some point in the future.

Kira Bindrim: So now I want to go back to birthrate, what impacts a country’s birth rate, the number of kids that people are actually having?

Tripti Lahiri: So one of the biggest ones that we’ve seen over time is education. Education, and the easy availability of contraception, and then those kind of go together. You know, to be able to access or asked for a contraception, you probably need to have some level of education and some level of confidence and ability to make choices, and then education really does lead to all of those things. There are cultural factors as well. To go back to Israel for a second, Israel has like a pretty high fertility rate, around three. And I think the last time the US had a similar number was back in the 1960s. So I think in Israel, there’s different things. There is social welfare that really does support women. and there’s work life balance, but also, there’s probably cultural historical factors that are leading people to have a higher idea of how many children they want to have.

Kira Bindrim: It’s interesting, because on the one hand, the idea of the replacement rate, even though it’s crude, is kind of obvious—there’s me, there’s my partner, we want to perpetuate the species, and so we’re going to produce offspring. But I’m curious where the idea of the replacement rate, or when it started to sort of enter our consciousness. Do we know who first sort of defined or articulated this as an indicator?

Tripti Lahiri: Yes, we actually do have an answer to that. There’s a pretty well-known-for-his-time demographer and economist called Robert Kuczynski, Robert René Kuczynski. And he published this two-volume edition called The Balance of Births and Deaths. And in it, he kind of tried to bring some rigor to concepts in the study of population. So he was like, ‘It doesn’t make any sense that you just look at the books in a year and compare it to the deaths in a year, if the births are more than the deaths, you’re like, “Oh, everything is fine.”‘ He was like, ‘You know, a birth is not equal to a death, because you need to think about the whole structure of your population. And you need to think about who’s going to be having kids in 15 years.’ And he actually looked at the numbers for Europe, and he felt that there was a concern there, that Europe was going to start declining at some point in the future based on those particular rates that it was recording.

What impacts a country’s replacement rate?

Kira Bindrim: So can you give me a few examples of countries that are dealing with replacement rate in different ways, and sort of the dynamics in each of those countries?

Tripti Lahiri: So, yeah, there’s a huge range out there. If you take South Korea, for example—South Korea is just an example of a really low fertility rate, well below replacement, I think it’s around one. And the government there is trying to improve benefits and address the issue and make it easier. But I think it’s no accident that South Korea is also recorded as being one of the places where like housework division is the most uneven (pdf). And so I think it’s almost like women are like, ‘This is just not tenable in the current scenario.’ So that’s one at the very low end of the spectrum.

But at the other end, like if you look at Israel, Israel is like a big anomaly in lots of ways, because it has a fertility rate of around three, at least in 2015. And so that’s above replacement. And I think the last time the US had such a rate was maybe in the 1960s. And what’s curious about Israel is like, it just goes against a lot of trends and other countries. So in other countries, often like more educated women are having less children than less educated women, and in Israel, that’s not true. It’s like, all the women are having children. So that’s a pretty interesting case, I think. And also women are having kids later, just like they are in other places, but that is not reducing the total number of children they’re having. So Israel is like, very mystifying. One of the things people attribute it to is possibly like this cultural, historical sense of like, you know, needing to have have a certain number of children.

And then coming to Africa. So Africa has traditionally not been one of the most populous places in the world. Like, if you look back less than 100 years, like to 1950, for every six Asians or two and a half Europeans, there was there was one African. But because fertility rates are still relatively high there, and though they will decline, they will take some time to do so. And that means that,  by the end of the century, there could be a lot of Africans, almost similar to the number of Asians, and a lot of them will be a young working-age population. So, you know, we keep talking about what a good thing that can potentially be for a region. And so, who knows, that could be really sort of transformative.

Kira Bindrim: Where do you see the conversation about replacement rate intersecting with bias or prejudice about who should be having children, and how many children people should be having? I’m thinking about this in the context of race and socioeconomics that we often see a lot of judgment of, having ‘too many children’ when it comes to marginalized communities. Is that a factor here? Or does that play into, or could it play into, conversations about the replacement rate?

Tripti Lahiri: There’s two ways to think about this. And one is we’re talking a lot about climate change at the moment, you know, we’re thinking about emissions. So from the perspective of what the fertility rate should be in different places, actually, it’s good that the fertility rate in the richest countries is going down, because those are the people, when kids are born there, they’re gonna add a lot more to that country’s carbon footprint than a kid born in so many other parts of the world. So that’s one thing to think about—the current fertility rates, the way they’re shaking out, it’s not bad from an emissions point of view necessarily. Or it could be worse, let’s say. But, yeah, there are ways in which these numbers can be misused or provoke anxieties. So I think in countries where there are conflicts between majority and minority groups, politicians can become very fixated on birth rates in groups that are already marginalized. And that’s very problematic. So yeah, you know, there can be that anxiety. And I think some countries, when they fixate on trying to get people to have more children, they do have an image of the country, and maybe they want to maintain that composition, to some extent.

Kira Bindrim: Sorry, I’m just stuck on the idea that all the rich countries should just stop having kids. Give it up. Tell me about China, because that strikes me as an example where the government stepped in and there was a policy, or there isn’t anymore, but there was a policy that directly affected the number of kids people could have. So I imagine that’s kind of a unique case.

Tripti Lahiri: China is pretty unique, because there probably isn’t another country that was able to, or could have implemented such a coercive policy for such a long time. And, yeah, that has really set in place a kind of fertility trend that they are now trying to reverse, and they’re having a very hard time doing it, because it changed so many things in the structure of the population, like, you know, the number of young women to men, or the total number of young people in a reproductive age. China’s fertility rate is 1.7, and the share of older people is growing a lot. And so they’re very, very worried that, in the future, young people are going to be taking care of two parents, and maybe grandparents as well. So that’s a big worry there. But one interesting thing I read about China is that, even before they brought in this coercive policy, they had a less, just like one that they broadcasted with health workers in every province, which was basically this kind of mantra of ‘Later, longer, fewer‘—so like, marry later, have longer gaps between kids, and have fewer kids. And actually, in that decade, fertility rate dropped a lot. So even to this day, people question whether China even needed to do the One-child policy or, like, they were educating people, and they would have anyways.

Kira Bindrim: To what extent do individual countries’ replacement rates matter? In other words, if some countries have high birth rates, and some countries have low birth rates, does that all even out in terms of the global population? And even just hearing myself say that, it sounds kind of naive, but could it be an answer? Or is it an answer to any extent right now?

Tripti Lahiri: I think it’s always been to some extent an answer, ever since it became a situation where people were having fewer than replacement-rate children, which is pretty recent. But yeah, countries like the US and Canada, and Australia—there are a lot of countries, the UK as well—their populations have been growing, although they’ve been below replacement rate for a while. They basically just turn to people from other countries, and that kind of brings in a flock of young people, and sometimes it’s a flock of young educated people that another country educated. So, from that perspective, it’s a pretty good thing for the receiving country.

Kira Bindrim: After the break, what do low birth rates mean for the population?

[ad break]

What happens when a country’s birth rate is lower than the replacement rate?

Kira Bindrim: I started this episode talking about overpopulation, and this idea that, if we have too many kids, the toll on the environment will be so great that quality of life goes down, or we all get shrunk into miniature sizes, or whatever. But I want to talk a little bit more and dig into the short-term implications of birth rates coming in under replacement rates. If we look at a country where the birth rate is two, or even below, where it’s low, what are the changes that brings within, let’s say, one or two generations? Because you’re really describing a reshaping of the generational breakdown of any country.

Tripti Lahiri: Well, so I believe if you’re around two, you would not be subject to a huge reshaping that you need to worry about. But what’s happening is, and I think a lot of economists or social scientists thought that the world would get to two and then stay there. But what’s happened instead is, in so many places, it’s actually just kept going down and down from there. That’s where you then do start to see a reshaping of a particular country’s age structure. And so I think another thing that people started to realize, and what replacement rate reflects, is that it’s not only the number of people that you have that’s important, like whether it’s in the world or whether in a particular country, but it’s also how are those people distributed in a lot of ages, because that really affects how your economy works. So, for example, if you have a ton of kids under five, or a ton of people older than 80, there are going to need to be more adults who can take care of them. Versus if you have fewer people in those age groups, and that means you have a lot of people with free time to work and whatever, be productive and add to society. So I think people have just realized that the age structure of a population is really important, too.

Kira Bindrim: It seems like there is an assumption here, a partial assumption, that having enough people and the right demographic mix kind of sets the country onto the right path, at least economically-speaking, in terms of its ability to serve all of its portions of its population. Is that generally the case? Like if I think about India, for example, demographically, there is a really robust younger generation that should be an asset, but we haven’t fully seen that realized in the economy.

Tripti Lahiri: So yeah, I think you’re talking about this idea—you’ve probably heard this phrase demographic dividend, right? And so the idea is that, oh, there’s this magic moment, a country has a lot of kids, and then at a certain point, those kids are in the workforce, and then you know, wow, boom, the economy’s gonna do so great and that country’s gonna jump forward. But that’s not a guarantee. It’s not like, oh, this many years later from having this number of children, suddenly your GDP grows up. Obviously, you have to do some things for those children, like feed them well, and give them a good education, things like that. And if you do not do those things, then that demographic dividend may never happen.

What countries should do to increase birth rates

Kira Bindrim: So it’s only the first step, having the kids, is what you’re saying. Okay, so let’s assume that sort of all nuance notwithstanding, it is understandable that countries would want to encourage a certain birth rate. When a government wants to encourage a higher birth rate, what do they do?

Tripti Lahiri: So they could do what Sweden did, or Sweden has done since like the 1950s or 60s, which is to make childcare very widespread, very affordable, a lot of kids under age five are covered by childcare. And so Sweden, you know, although it’s not a replacement rate, it does have one of the higher fertility rates in Europe, I think it’s around 1.7. And, you know, if you then have some immigration going along side, then your population structure might be pretty good, because you have your 1.7, you have good health, so all those kids are growing up. And then you bring in a certain number of people every year toto get you those extra adults that you want to have in your population. And, yeah, it’s a pretty good situation. And France, to some extent, also has had very good policies. So they also have a 35-hour work week and things like that, work-life balance and parity between the sexes helps.

Kira Bindrim: Is there anything countries should be doing that they are not doing, or not doing enough of?

Tripti Lahiri: So I did read this one interesting overview of fertility policies (pdf). And one thing that it said is that sometimes governments bring in fertility incentives, but then suddenly the next government comes and they take it away. And this kind of creates a lot of like confusion and upheaval, and this is not helpful at all. So I guess, if you don’t know what you want to do, better not do anything. I guess that’s one thing. And then oftentimes, benefits are pegged to a woman’s last earnings, or parent’s last earnings. And so you know, if you’re in a gig economy, or you’re working part-time, those incentives do not help you very much. And if more people are going to be working like that, then governments should think about how do we help those people when they want to have a child

Kira Bindrim: So unless you sort of come at the systemic issues that come with having kids and raising kids, it kind of doesn’t matter how many kids people are having this, maybe a very reductive way of summing all this up, but one way to think about it?

Tripti Lahiri: Yeah, I think you do have to really think about, how do you help people with childcare? Especially if women are like, ‘I don’t want to give up my career,’ or ‘I don’t want to earn less over my lifetime.’ So many incentives today are also built around marriage, but marriage is also declining in many places. So, can we have incentives that respect the different ways people want to live now, not necessarily with what the same person forever, and yet somehow manage to make it possible to raise children?

Kira Bindrim: How do you square the idea of individual choice and national responsibilities? To me, I kind of liked the idea that, by not having kids, I was saving the plane—that something that made me feel quite self righteous. But now you’re telling me that maybe I’m contributing to the deterioration of the United States, and maybe the future of humanity. So it’s a lot to internalize, Tripti, and how you think about that?

Tripti Lahiri: Well, I sometimes think that, as somebody who probably has a big carbon footprint, I don’t have children, but I think, probably that’s been good for the planet. And I also think that given how much the population is still going to continue to grow, it’s probably not a bad thing for countries to get below replacement rate and then maybe later on try and change those trends a bit once the population of the world has come down or stabilized. I think that having individual choice is so great. I think it’s amazing that women can just be like, ‘I do not want to do this,’ and not do it. And I really think that should be front and center of how countries think about this,. and that no one should feel like they have to get married or have children for the good of the nation. I think that that’s really like a lot of pressure to put on any person.

How will current birth rates impact future generations?

Kira Bindrim: And then make sure you have a girl because otherwise you didn’t adequately replace yourself. Okay, let’s take all of this and I want to just throw it forward, spin it forward a little bit. If our current trends hold, birthrate trends, what can we expect the world to look like, like 200 years in the future? How will that play out?

Tripti Lahiri: So nobody can predict anything 200 years in the future.

Kira Bindrim: I won’t hold you to it.

Tripti Lahiri: I just want to tell you about this guy, Malthus. He was an economist back in 1798, or he was also a priest, I think. And he was like, ‘The world is going to explode and everybody is going to starve.’ And then a bunch of people left Europe and went to America and did get more food. And then also, agricultural technology changed. So, it’s very difficult to predict. And even people who do it well, like the UN Population Division, their chart of the future, it’s like a broom, like there’s one estimate at the bottom, and then another estimate at the top, and they’re like, ‘Yes, the future could top out at, like, 8 billion people, or 12 billion people.’ So no one knows anything. But I’m just gonna tell you what the UN thinks is its most likely forecast: They think that, by 2050, the world would have maybe 9.7 billion people. And then we’ll stop growing around like 10.8 in 2100.

Kira Bindrim: What is the big lesson here? Like, if you want everyone to come away thinking something, having learned something about the replacement rate, other than what it is, what is the takeaway?

Tripti Lahiri: I think that for me, one of the takeaways is the power of education and giving women more choice. Let’s take India—they’re supposed to be at replacement rate, or even below now, and a lot of people, a lot of estimates, predicted that would happen later. This is the result of women having more control. For me that’s one takeaway, just the power of individual choice.

Kira Bindrim: It’s amazing how many topics, the take away is just ‘give women more control.’ I think that this is our next podcast.

Tripti Lahiri: Seriously, though, the world is so much better when women can just say no.

Kira Bindrim: Okay, I have one last question for you. I just want to know the most interesting thing you’ve learned in the course of your research. What is something you cannot get out of your head?

Tripti Lahiri: I just can’t get over the fact of how much older the world is going to be in the future—and not even the distant future, like in the next 70, 80 years. I think right now, the median age is around, I want to say 24 [EDITOR’S NOTE: median age is now closer to 31]. And later in the century, the median will be something like 40. So just imagine that. And I think around 2070, there are going to be possibly more people over age 65. So everyone born up to 2005 who continues on in life, they’re going to outnumber the people who are under age 15. That’s kind of like, what is that going to be like?

Kira Bindrim: I don’t know if I hate it, because I’ll be in the majority and we’ll have sort of domination over the youth. I could work with that.

Tripti Lahiri: Well, I may be dead by the time some of this happens. But yeah, I would like to stick around. I would be interested to see, to be around in the year that it’s like, ‘Oh, yeah, this is the population, it stopped growing, we’re not growing.’ That’d be pretty cool to see.

Kira Bindrim: It would be interesting. There would probably be a big blockbuster movie about it being scary. Thank you so much, Tripti. This was super fascinating.

Tripti Lahiri: Thank you, Kira. I had fun chatting with you about this.

Kira Bindrim: That’s our Obsession for the week. This episode was produced by Katie Jane Fernelius. Our sound engineer is George Drake and our executive producer is Alex Ossola. The theme music is by Taka Yasuzawa and Alex Suguira. Special thanks to Tripti Lahiri in New Delhi, as well as Stuart Gietel-Basten and Tomas Sobotka for research help.

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