Population Decline Is Worse Than You Think | Prof. Dean Spears

More good lives are better than fewer good lives, and the absence of billions of potential good future lives would represent a loss to mourn, not something to celebrate

“one path is a path where many billions of additional lives could get to be lived that could be really good and wonderful and valuable and full of happy experiences for the people who live them. And so, one question we should ask is is would the absence of those lives be, you know, would it be a nothing? Would it be something to celebrate or would it be a loss to mourn because of those experiences in it?”

Two-thirds of the world's population currently lives in countries where the birth rate is below two children per two adults (replacement level), which is the threshold for depopulation.

“twothirds of people worldwide live in a country where the birth rate is below two children per two adults”

Energy and carbon emissions have begun to decouple in many places, meaning population and energy growth no longer automatically translate to carbon growth, as renewable energy and efficiency improvements allow continued material improvement with lower emissions

“Climate seems like a fairly to me at least a fairly cut and dried one because we are starting to see the decoupling between um energy and carbon emissions. So even if the population grows and energy usage grows over time the the carbon curve should at least sort of start to level off and and even decline.”

The median age of the US population increased by 9 years from 1950 (age 29) to 2025 (age 38), and is projected to increase by only 7 more years over the next 75 years to age 45, meaning future aging will be slower than past aging despite depopulation.

“the median age in the US population um in 1950 I think was 29 um and inc is in the 75 years since then has increased by nine uh age years um to 38 and is projected um over the next 75 years over an equal span to increase by seven age years to”

Social Security and other retirement systems were designed to support the elderly when there were many working-age people per retiree (approximately 9 to 1 historically); depopulation will invert this ratio, creating an unsustainable fiscal burden unless taxes on workers increase radically or benefits decrease.

“the Social Security Administration was introduced in order to try to take care of elderly people who are in desperate poverty. We don't want elderly people to be starving to death and horribly neglected medically or financially. Um, and we've been able to support elderly people in our civilization when we have a handful [1:00:53] of working people who are able to support each elderly person. I don't know what the number is right now. Maybe it's three or four working age people for every elderly person who's retired.”

China has a birth rate around 1.0 (half of replacement), and although economically heterogeneous and middle-income, its fertility is equivalent to or lower than wealthy countries.

“China is a heterogeneous middle- inome country, but you know, it's at one.”

South Korea currently has the world's lowest birth rate at 0.78 children per woman, meaning that within two generations the country will have one-seventeenth the number of babies it has today.

“the lowest is South Korea, right? It is currently at 0.78. Yeah. Exactly. And and just to like for us to rock what that actually means, it's that in two [7:19] generations time, North Korea, sorry, South South Korea, um although North Korea is also declining, by the way, which is interesting because they're so economically different. Um, but within two generations, South Korea is going to have 17th the number of babies that it's having today. 17th.”

The US birth rate remained relatively flat around 2.0 for 35 years (1975–2010), an anomaly that no researcher fully understands; before and after this period, the rate has been falling.

“So, the US has been a bit of an exception to this global trend in falling births. Not that the birth rate hasn't been falling in the US, it certainly has been. Um, but for 35 years or so, from say 1975 to 2010, it was relatively flat in the US around two. So, that was a a time when a lot of things were changing, a lot of progress in a lot of dimensions. Um, but the birth rate in the US was relatively flat [8:51] and it's a bit of an anomaly. I don't think that anybody fully understands why that's the case in the US during that time.”

Median age in the US has increased 9 years since 1950 (from 29 to 38), and is projected to increase 7 more years over the next 75 years (to 45), meaning the magnitude of projected age increase is smaller than the historical increase that already occurred.

“the median age in the US population um in 1950 I think was 29 um and inc is in the 75 years since then has increased by nine uh age years um to 38 and is projected um over the next 75 years over an equal span to increase by seven age years to”

People's fertility behavior shows both adaptation and path-dependence: fertility declined during COVID despite people having more time at home, suggesting structural economic uncertainty (job loss, healthcare system strain) matters more than scheduling constraints.

“from what I've seen, it was actually kind of the opposite. Uh, fertility rates went down even further during CO. It was actually quite a re I mean, there might have been a slight peak, but overall 2020 to 21, they I think a lot of nations reached their lowest fertility rates historically, which is interesting.”

Latin America has a birth rate of 1.8, and the narrative that fertility decline is limited to wealthy countries versus developing countries is misleading

“Latin America is at 1.8. Um, you know, we've already talked about India. Um, um, you know, other places, you know, Nepal, Bangladesh, they're falling too.”

There is currently no toolkit, plan, or automatic stabilizer that would reverse depopulation once it begins; society has no policy lever to bring birth rates back up without addressing underlying opportunity-cost structures.

“The most interesting part is that there's no toolkit that anybody currently has, no plan, no automatic stabilizer that would bring us back up.”

Younger voters tend to be more environmentalist than older voters, so a depopulation-driven shift in voter age composition will change voting patterns on environmental issues, with uncertain implications for environmental policy

“we know that younger voters tend to be more environmentalists than older voters. Um, and so, you know, that's one thing that might shift as as the age structure population changes.”

The year with the most babies born globally was 2012, when 146 million babies were born; births have been declining every year since, even though world population has not yet peaked because mortality rates continue to fall.

“We've already passed the point, the year when the most babies were born. That was in 2012 when 146 million babies were born all around the world. And ever since then, it's been lower and it's declining.”

Mortality rates are falling toward zero and cannot fall further, so the only source of future population growth must come from birth rates rising, not from further mortality declines.

“of course, the probability of dying in childhood can't fall below zero. So, we'll never get that advantage again. We'll never get that source of population growth again. Um, you know, it'll fall to zero and [5:42] stay there.”

Pre-adult mortality (death before age 18) was much higher historically, meaning replacement fertility rates would have needed to be higher—perhaps 3 in high-mortality areas versus 2 in low-mortality areas—because many children would not survive to adulthood.

“the replacement birth rate might be a number closer to two for a state in the south like Carerala but closer to three for a state in north like Utra Pradesh where pre- adult mortality is is greater”

There is significant evidence that the pandemic (2020-2021) reduced fertility rates globally rather than increasing them; most nations reached historically low fertility rates during COVID, contradicting the expectation that lockdowns would increase births.

“from what I've seen, it was actually kind of the opposite. Uh, fertility rates went down even further during CO. It was actually quite a re I mean, there might have been a slight peak, but overall 2020 to 21, they I think a lot of nations reached their lowest fertility rates historically, which is interesting. It's not a great time to be in a hospital.”

South Korea currently has a fertility rate of 0.78 children per woman, the lowest globally, which means that within two generations South Korea will have 1/7th the number of babies it is currently having.

“It is currently at 0.78. Yeah. Exactly. And and just to like for us to rock what that actually means, it's that in two generations time, North Korea, sorry, South South Korea, um although North Korea is also declining, by the way, which is interesting because they're so economically different. Um, but within two generations, South Korea is going to have 17th the number of babies that it's having today. 17th.”

AI and automation may complement rather than substitute for human labor, increasing human productivity rather than replacing humans; this would strengthen rather than weaken the economic case for larger populations.

“for this sort of discovering things work that people do you know AI might turn out to be a substitute for humans or AI might turn out to be a compliment for humans and increase the productivity of other people. Lots of other technologies have been compliments for humans. Right? So when um when spinning yarn when was mechanized right that was a substitute for what humans did nobody did that work anymore right but when um but when um [40:33] you know factories themselves with powered by water came online that was a compliment for human productivity and made humans more productive.”

People create demand for specialized services and goods (schools, hospitals, entertainment, infrastructure) that AI cannot replicate; other humans wanting and needing things you want and need makes you better off economically and socially, independent of whether AI could theoretically fulfill those functions.

“when other people want and need the same things that you want and need, they make it more likely that you'll get it. um you know where are you going to find you [37:51] know uh u an event like this in a space like this? Are you going to find it in a city with other people in it or in a depopulated rural place? Well, of course you're going to find it in a city with other people in it, right? Other people make it possible for the things that you want to happen.”

Building support systems for caregiving and parenting—reducing childcare burdens, enabling flexible work, improving parental support—could shift what people perceive as a 'good life' such that future generations would aspire to parenthood and larger families, even without explicitly changing fertility preferences.

“if we were in a really big way going to invest in taking better care of our caregivers, doing more to share the work and making the next generations dads doing more to share the work and making the next generation, then maybe we would see more people feeling like they could fit that in to the life and goals and education and work that they want. And probably not immediately, but maybe the next generation after that would learn from that example and the next generation after that would learn from that example. And then maybe people would start wanting something different.”

The opportunity cost of having children—what one gives up to have a child—has increased dramatically as work quality has improved, entertainment options have expanded (especially through technology), and the pleasantness of not having children has increased, while the discomforts of parenting have not substantially changed.

“We live in a world where a lot of things are getting better. If what you like is work, work is getting better, especially if you're a woman relative to a few decades ago. If what you like is play, play is getting better. If what you like is just sitting doing nothing, then now you have playing video games. Yeah. You have a washing machine and a dishwasher to do your laundry and wash your dishes. And you know, doing nothing is better, right?”

Many people value the existence of other people's good lives (moral concern for future generations, preference that more people get to live good lives rather than fewer), which is a reason to care about population size independent of economic effects.

“to give my answer, I would say that I think that, you know, more good is better and that that includes the good of getting to live a good life and have good and happy experiences. um and that it that it does matter that um you know if people don't get to live those lives now to say yet again the fact that something matters doesn't mean that it's the only thing that matters and it doesn't mean that we should you know take away people's choice or impose it on anybody but when we're thinking about which path should we build towards over the long run perhaps one of the things that we should be asking is is it better if more people get to live and experience good lives rather than fewer”

Stabilizing population at a lower level (e.g., 2-3 billion) would still require reaching replacement fertility of 2.0 children per woman, so avoiding the question of how to raise fertility back to 2.0 by choosing to depopulate to a smaller population doesn't solve the underlying policy problem.

“If you think that we should stabilize the size of the population at some level someday, then you're on the team of needing to find a good path to an average birth rate of two, needing to raise the birth rate at that someday up to two. is stabilizing the population at any level, even a level much smaller than today, will someday require an average birth rate of two.”

A larger population with a larger economy can generate greater negative emissions capacity (planting trees, rock weathering for carbon sequestration, etc.) than a smaller population, so under some climate models, larger population in the long run leads to lower temperatures once the world reaches net-zero carbon emissions.

“we were saying in that model what if we vary the path of the population you know then how much of a difference does it make to climate change and that like peak temperatures and the answer is not very much um but we sort of discovered by accident and I sort of like I I first thought that like the the posttock research scientists on our team have made a mistake. were like, you know, Kevin, go back and look at this again. But like, in fact, the larger population ultimately leads to lower temperatures in the long run. And it's because the model did allow for these negative emissions where, you know, a larger economy that's doing more can plant more trees, split up more rocks, whatever it is.”

A larger population increases the probability of finding compatible partners, friends, and collaborators across all dimensions (romantic, professional, creative); a smaller population reduces relationship diversity and access to rare skills or interests.

“Usually we like the people around us and the more [1:17:28] people we have, the kind of like more fits and better friends we can also find and better partners. You know, the whole like is there someone for everybody? Well, not if there's only like uh very few people than there are like some very good ones, some very bad ones.”

Even if perfect reproductive technology (a 'baby button') were available, it would eliminate miscarriage and infertility but would likely not raise fertility because the cost-benefit calculus of parenthood happens after childbirth; the technology would make existing plans feasible but would not make people want more children than they currently do.

“an awful lot of the costbenefit decision of whether or not to have a kid happens, you know, after the baby comes out and is on the outside. Which is not to say that pregnancy and child birth and um are not, you know, painful, harmful, risky, [21:50] and bad in many ways. Um and it's not to say this wouldn't make people's lives a lot better, but when you look at survey data of of, you know, people, you know, in their 40s, right, not that many people say that they want that many more kids.”

A larger world population with higher GDP would be better positioned to solve large-scale fixed-cost problems like negative emissions technologies, asteroid deflection, or pandemic response than a smaller population, because the solution costs are shared across more people and productive capacity.

“we're going to have a big negative emissions problem that that will have [34:44] reached, you know, zero per person net emissions and Then we have the negative emissions problem of needing to suck the carbon back out of the atmosphere. And so what do you think is who's what's going to what's going to do a better job of that, right? A bigger or smaller world economy.”

All 16 major demographic groups in India (Hindu, Muslim, rural, urban, educated, uneducated, etc.) have below-replacement or falling fertility rates, with no group sustaining above-replacement fertility, suggesting fertility decline is universal rather than group-specific.

“you can split India into 16 different groups you know Hindu Muslim rural urban educated noted educated whatever you get all 16 lines you know some are higher and some are lower but all 16 lines are going down right so they're not all below two yet Um but you know people in India like Hindu politicians in India used to say oh Muslims have more babies than Hindus do right um and Muslims do have more babies than Hindus do but it's gone down for Muslims and it's gone down for Hindus”

Certain large-scale existential risks (asteroid impacts, pandemics requiring vaccine development) have high fixed costs and are more likely to be managed effectively by larger populations with more scientific capacity than smaller populations.

“let's say an asteroid was coming to Earth. Which population size is more likely to actually deal with it? 10 billion people or 1 billion? Like given it's going to cost, let's say, 10 trillion or some huge proportion of GDP?”

India currently has a birth rate below two children per two adults, and young women even in the poor state of Uttar Pradesh (where Spears conducts research) say they want an average of 1.9 children.

“My research is about India. India is below two now. Um and even young women in the poor state of Utra Pradesh where I work say that they want an average of 1.9 kids.”

Low and falling birth rates appear to be a convergent phenomenon—many different headwinds work against having large numbers of babies—rather than driven by a single cause like capitalism, religion decline, marriage decline, or female labor force participation, as exceptions exist for each single-cause theory.

“low and falling birth rates seem to be a convergent phenomenon. That's something where there's a lot of a lot of headwinds against having a lot of babies. And so so that's theoretically important.”

Of 26 countries where completed cohort fertility (lifetime average births per woman) has ever fallen below 1.9 since the mid-twentieth century, zero of them have ever seen fertility rates climb back up to two.

“of those 26 that have ever had completed cohort fertility fall below 1.9, zero of them has it ever gone back up to two. Um, and so, you know, that doesn't mean that it's impossible, but it means that there's not a precedent that we can draw on.”

Other people wanting and needing the same things you want and need makes it more likely you'll get those things (e.g., schools, hospitals, specialized treatment); demand from other people creates supply, so a depopulated world might lack services and infrastructure because there is no demand for them.

“part of the case for people is that they want and need things and sort of they economically demand things, right? Like you want there to be other kids who like if you're like a parent, you need there to be other parents so that your kid can have a a school, right? And and like you need other people to to need the things you need. you know, when my mom was sick with a rare form of cancer where where we lived in Oklahoma, there wasn't, you know, well, first of all, only 640 people had ever had that cancer uh since the 1970s. So, nobody knew anything about it. But even in order to learn that, we had to drive to a big city where there was a hospital where there would be a doctor who would even sort of know that fact, right?”

Most of the global fertility decline is attributable to people who have children having fewer children (smaller family size) rather than to increased childlessness, though the US is an exception where childlessness is a larger component.

“if you sort of break it down to the into the accounting more of the difference is globally is about people um u having fewer kids who have them. This is a case where the US is a little bit of an exception and the increase in childlessness is a bigger part of the picture for the US overall.”

Climate change is manageable on the time scale of depopulation because decarbonization can occur within decades, whereas population decline takes centuries; by the time a child born today reaches reproductive age, carbon solutions should be largely implemented.

“climate change is just too urgent...If you have a baby today, by the time that baby grows up and is deciding whether or not to have babies, you know, enough decades will have passed that we'll be at that point.”

The dichotomy between career and children is a modern invention tied to industrial, 9-to-5 work structures; pre-industrial families operated with all members contributing to household production (farms, stores), allowing children to be integrated into work without the modern conflict.

“I actually feel like there's this perceived dichotomy for many women that I've spoken to where either you get to have a fulfilling career or you get to have children, um, have a vocation or have children. But I just feel like our ancestors simply did not have this perceived dichotomy. pre-industrial life, everyone contributed. And the concept we uh that we now have, the 9to-5 career only really existed after the invention of the assembly line.”

Freak's argument for depopulation relies on false zero-sum thinking that ignores human innovation and technological possibilities; this kind of reasoning historically leads to dark policy outcomes because it forecloses human agency and adaptation.

“it's it's it's a form of false zero sum thinking um which can be incredibly damaging because it's it's if you make policies based on the fact that oh this is a completely fixed pie and there's nothing we can do and we can only divide it up and you're just neglecting all the sort of well frankly known unknowns but even unknown unknowns that can come through [33:11] human innovation and that's where you end up in these really dark places I think um quite regularly.”

The question society should be asking is whether depopulation (each generation smaller than the last) is the future we want, or whether we should instead aim for stabilization; most people have not yet been presented with this framing.

“what we talk about is you know the question that we should be thinking about is is this sort of depopulation generation after generation is that the future that we should want for the world or should we instead should we let that happen by default or [4:10] should we instead want the population to stabilize?”

Reducing female education, making society poorer, or increasing infant mortality would reduce opportunity costs and increase fertility, but these would be catastrophic solutions and not acceptable responses to fertility decline

“if I was to take the economics lens and like the other way to reduce the opportunity cost like if I was super villain and I wanted more babies I reduce female education. I make us poorer and we have more baby and I increase infant mortality and we have more babies. Terrible answer. Let's not do that.”

As the global average birth rate declines and approaches zero, variance across countries necessarily shrinks because birth rates cannot go below zero, so high-fertility outliers will become less possible.

“just like I said death rates can only go down to zero I mean birth rates can only go down to zero and so there's a sense in which the variance has to be shrink shrinking as the average goes down.”

The US Physician Recommendation (ACOG policy) explicitly advises against offering young women AMH (anti-mullerian hormone) blood tests to assess ovarian reserve, which could help women plan family timing but is discouraged as potentially causing undue stress

“my understanding is the American OBG Association recommends that physicians not offer women a blood draw for AMH antimmalarian hormone that would indicate ovarian reserves because it can cause them undue stress.”

Younger voters tend to be more environmentally concerned than older voters, so demographic aging (more older voters) will shift voting patterns in a less environmentalist direction unless fertility increases

“we know that younger voters tend to be more environmentalists than older voters. Um, and so, you know, that's one thing that might shift as as the age structure population changes. We, you know, we should expect, you know, voting patterns to shift with it.”

Post-AI society could reorganize work to be less dependent on the 9-to-5 model, potentially allowing both careers and childrearing, particularly if automation reduces the need for full-time centralized employment.

“with AI...Do we need that anymore? And so, um, I feel like that's largely not conducive to family systems. And it's funny that you brought up South Korea cuz I spoke to a diplomatic delegation from Japan and South Korea of women in STEM and they couldn't even fa most of them couldn't even fathom the concept of having children in the workforce. And then one person in the room, I forget like which country she was from, but she was talking about during the pandemic, they did and it kind of changed everything for her.”

The current period is analogous to the early stages of climate-change policy (1960s–1980s), when the problem was recognized but not yet solved, and premature policy prescriptions would be counterproductive; instead, society should now focus on understanding the problem and building consensus that stabilization is preferable to depopulation.

“six decades ago um was the 1960s when there was you know first starting to be some policy attention to climate change as a problem. So, you know, Johnson gave a speech to Congress about burning fossil fuels and and you know, that wasn't the beginning of people collecting data on it like Arinius had done like atmospheric chemistry calculations that were pretty close to true even before then. But I think there was something notable about what people were thinking and talking about six decades ago. Um, and you know, six [45:13] decades ago, if at the beginning of the climate policy conversation, somebody had just stood up and sort of spouted off whatever policy prescription happened to come to their mind, it probably would have been ridiculous.”

Many specialized medical treatments exist only because enough people need them to justify the cost of developing and maintaining them; a depopulated world would have fewer incentives to maintain specialized services like rare-disease treatments or niche infrastructure.

“you know, when my mom was sick with a rare form of cancer where where [42:07] we lived in Oklahoma, there wasn't, you know, well, first of all, only 640 people had ever had that cancer uh since the 1970s. So, nobody knew anything about it. But even in order to learn that, we had to drive to a big city where there was a hospital where there would be a doctor who would even sort of know that fact, right? If what you need is specialized treatment, you need other people who need that.”

If the world population peaked and then declined to 1 billion over several centuries, the infrastructure built for 10 billion (schools, hospitals, utilities, housing, roads) would be massively oversized and economically inefficient; this represents a colossal waste of resources and capital.

“within two generations, South Korea is going to have 17th the number of babies that it's having today. 17th. So, if you just imagine what that looks like, it means that all of that infrastructure they have right now, ch, you know, schools, um, playgrounds, all these things that we associate with children, it's going to be like ghost schools, ghost playgrounds, because you're literally [7:49] going to have empty classrooms.”

The conversation about population decline and stabilization should begin now, decades before the projected population peak in 2084, to allow societies time to gather data, develop understanding, and build social movements, similar to how climate change discourse took 60 years to develop from initial warnings to current policy focus.

“the hope that I see is that we're starting a conversation now um you know several decades before the size of the world population is projected to peak and you know more people are going to learn and talk about this between now and then learn the facts start thinking about what might be different”

Fertility decline is driven by convergent pressures and not by a single factor; therefore, solving fertility decline will require addressing multiple factors simultaneously rather than single policy interventions

“if we do think it would be better for the population to stabilize, we shouldn't think that any sort of, you know, quick fix is going is going to be what changes this.”

The opportunity cost of having a child has risen dramatically because alternative activities—work, leisure, entertainment, comfort goods—have improved, while the intrinsic non-economic rewards of parenting (waking up at 3 AM to clean vomit, ongoing responsibility for decades) have remained relatively constant.

“So, you know, the opportunity cost is what you give up to have something. The opportunity cost of a kid is what you give up to have a kid. And so, we live in a world where a lot of things are getting better. If what you like is work, work is getting better, especially if you're a woman relative to a few decades ago. If what you like is play, play is getting better. If what you like is just sitting doing nothing, then now you have playing video games. Yeah. You have a washing machine and a dishwasher to do your laundry and wash your dishes. And you know, doing nothing is better, right?”

If societies decide to pursue population stabilization, they should do so by expanding support for caregiving, making parenting more compatible with work and education, and sharing caregiving costs across society—not through coercion or by narrowing reproductive freedom.

“you can be a person who cares about environmental stewardship, who cares about reproductive freedom, who cares about gender equity, who cares about all sorts of priorities, and also care about birth rates and the size of the future population.”

The problem of climate change is 'easier' to frame and solve than population because it has more urgent timescales (2030-2050 decarbonization targets) compared to population stabilization which operates over generations

“I mean I think you know on on climate change as you say that's sort of an easy one because it's just a a matter of timing. Um you know we need to decarbonize relatively quickly. Some people say years like 2030, some people say years like 2050.”

Sub-Saharan Africa currently has an average birth rate over 4, down from 5 a couple decades ago and 6 a couple decades before that, with fertility expected to continue declining as female education increases (consistent with pattern in India and Kenya).

“subsaharan Africa, somebody might say, what about birth rates in subsaharan Africa? on average a little bit more than four right now. Um but you know that's down from five a couple decades ago and six a couple decades before that. And you know female education is still pretty low in subsaharan Africa. Um so if you you know if you know India which is around two is maybe around 3/4s of of high school age girls going to school. Um you know Kenya is a higher birth rate around three. It's maybe around half of girls going to school. place like Mosmb beek has a higher birth rate and you know and you know maybe around a third of girls going to school and so there's every reason to think that as subsaharan Africa traces that socioeconomic development pathway that we've saw for example in India birth rates there will fall too”

AI might either substitute for human innovation and labor (making humans less necessary) or complement human productivity (making humans more productive), but under the complementary scenario, the case for population becomes stronger, not weaker.

“for this sort of discovering things work that people do you know AI might turn out to be a substitute for humans or AI might turn out to be a compliment for humans and increase the productivity of other people. Lots of other technologies have been compliments for humans. Right? So when um when spinning yarn when was mechanized right that was a substitute for what humans did nobody did that work anymore right but when um but when um you know factories themselves with powered by water came online that was a compliment for human productivity and made humans more productive.”

Some individuals report that having one child is manageable as an accessory, two children becomes a circus, and three or more becomes chaotic, implying that people's experiential assessments show declining quality of life with more children, not rising

“you have one kid, it's an accessory, you can get by. You have two, it's a circus. And then three, it starts to get crazy, right? And I think hidden in the data is people's choice is that I have a better life, a more fulfilling life with less kids.”

Currently, no toolkit, plan, or automatic stabilizer exists that would reverse population depopulation once it begins; the world has not developed mechanisms to raise fertility back to replacement once it falls below.

“there's no toolkit that anybody currently has, no plan, no automatic stabilizer that would bring us back up.”

There is a possibility that depopulation, if severe enough, could eventually force humans back into poverty and higher fertility through desperation (as happened historically when mortality spiked), but this is not a preferable solution path and we should not depend on it.

“So, I mean, we have our graph like you might have like seen the picture that we drew in the New York Times article where we basically say, okay, total fertility rate of 1.6, go. And it, you know, goes on forever and ever. And, you know, people write in to say, well, of course, you shouldn't think that's empirically what will actually happen. And you know indeed not right it's um it's sort of an it's the answer to an if then question. If the birth rate you know goes to a number like 1.6 then this is what you'd see. No I don't think that the population would follow that path forever. I think you know eventually as you say something important would break um and and we you know would no longer be able to follow that if then anymore.”