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Another consideration is the ongoing research on extending/prolonging lifespans. If successful, I would expect birthrate to plummet, and child-centred cultures to diminish. (And to our detriment, in my opinion.)

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That is the "Old Moms" scenario.

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Aug 24, 2023·edited Aug 24, 2023

Not necessarily. Sufficient life extension directly prevents populations from falling anywhere near as quickly as described, because the older people themselves are also still around. Under present conditions, if we eliminated all deaths from causes that mainly afflict the elderly (aka by indefinitely keeping the body at a ~35-yr-old level of health) , then lifespan would shoot up to well over a millennium on average. Then, with no older moms at all, almost everyone alive in 2100 will still be around in 2500, plus their next 16 25-yr generations of descendants.

As written, you're measuring generation cohort size via lifetime fertility as a proxy. Life extension changes how that relates to total population in a very different way than just allowing 60 yr olds to have babies and then live to 100 would.

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The Old Moms scenario requires that women bear children when they’re older. Increased longevity and vitality could also reduce the relative lifetime cost of delaying a career. With long enough lifespans, people might typically have several phases of what we now call careers, and delaying the start of the first by a decade or more might have far lower consequences for women.

More generally, longevity improvements reduce the overall burden of child-rearing, at both the individual and social levels. A gap decade might be a normal choice, for example, and not need to be enforced via taboos.

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The trouble with most scenarios is: The Hegel. Thesis-Antithesis. Development A will lead to change B which will affect A. But extrapolation is fun, as is nitpicking; thus my 11 nits:

1. Extinction: see Hegel: less kids - less people – more space – more kids. If I had 3 bedrooms more, we had 2 kids more. Also more gas, land, power per person – makes people richer (see Europe's boom after the plague); richer and more space= more kids (see 2).

2. Poverty: Nationally in the west, TFR is a U-curve, the poorest AND richest have more kids. The richest have most. - That said, one wonders what will happen in Pakistan and Nigeria this century.  

2. Big War: More poverty, sure; more kids: maybe, but much lower survival rates if Civ. + health care crashes + high radiation, possibly. HC may often be a „wasteful signal“, but for mom+kid surviving birth, it actually has some use - https://ourworldindata.org/maternal-mortality#where-are-women-most-at-risk-of-dying-in-childbirth .  

3. Old Moms: Sounds like more will have a kid, but mostly ONE kid. More mature mothers are more „responsible“.

4. Frozen Eggs: See 3. Mostly an excuse to delay kids „till the 12th of never“!

5. Robot Nannies: Yep, nice. But robot-wifes/hubbies might be much easier to do – total fertility crash in a generation. ;)  

6. DNA Selection: Given time and evolutionary pressure (TFR is BIG pressure!), this is my No1 scenario. Bryan Caplan is „dark triad“? As me (5 kids)? Conformity is no issue when all those child-less died out.

7. Insular Subculture: Amish, Mormons, orthodox Jews are doing fine – and a billion muslims. Not so insular, maybe. 

8. Parenting Factories: lol. AI-kids are even cheaper – and they shall call in as often as you like! Though I like the efficiency gains at this family of 181: https://en.wikipedia.org/wiki/Ziona#:~:text=Zion%2Da%20(76)%2C,state%20because%20of%20the%20family video (when they were only 175): https://www.youtube.com/watch?v=CX4H0mn0qKA

9. Gap Decade: Too expensive. And the non-kids-crazy will just travel the globe + tik-tok.

10. Gender Roles: that seems the most far-fetched, but see 6 and 7.

11. Nation Subsidy: Sounds more efficient than 9. Say 500k for 1 kid, 50k for each more should cover the opportunity costs for most. Might be well be worth it, if those kids are „high-quality“. Big IF.

12. Kid Debt/Equity: Actually a lot like 11. Private investors might be much better in finding the „right rate“ for each kid: „This will return just 1 million over a lifetime, we pay 20k now for the right of 10% of his income - incl. dole.“ „This one is high-value, as parents are obviously doing fine, we will invest half a million by providing a ‚free‘ nanny and a place in a 'Chinese kindergarten'.“

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This resonates. It seems like a lot of the trends may modulate rather than continue monotonically.

Many of those scenarios are not really captured by Professor Hanson's list.

One that seems entirely left out is professional cultural expectations. Perhaps parents will succeed in shifting expectations / norms around having kids or raising kids, in such a way that having a career is even more compatible with having kids than it is today.

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I was trying to list scenarios with mechanisms for their change. Just saying that expectations change isn't saying HOW they change.

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I find myself confused. I intended Professional Cultural Expectations to be a suggestion for an additional mechanism for the change in fertility rates.

Are you saying that you'd like me to elaborate on:

a) how a change in professional cultural expectations would come to be?

b) how a change in professional cultural expectations would impact fertility?

c) something else?

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a)

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Gotcha. There are many ways that such a cultural change may occur, but the core of it would be that top talent wants to have children, and they start to influence professional culture by some combination of a) lobbying for change, b) starting firms / companies that enable them to live the life they want, c) vocally leaving jobs that aren't "family friendly".

This could then cascade into a general trend of firms adjusting their behavior in order to remain attractive to top talent. Previously this occurred via higher remuneration. In the future this might be family-friendliness.

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> If world fertility averaged 1.4 for 1660 years of 25-year generations after a peak of 10B, humanity would go extinct. If fertility averaged 1.0, that would take only 830 years.

830 years??

I definitely don't expect current projections to be valid 830 years from now. We're gonna be robots, or vat-grown genetically engineered organisms the size of mice, or expanding through the galaxy with warp drives, or all dead. The most likely outcome apart from "all dead" is that AI will take over, and projections from that point will be determined by what the AI wants to do.

If regular biological evolution plays a role, this comic comes to mind: https://www.smbc-comics.com/?id=3130 The idea is that to have a ton of children you have to be able to make a lot of money to be able to raise them, and want to do that. So we may see some "hyper-fecund mega-nerds," with lots of money and lots and lots of children, and this phenotype could become dominant in the long term. We do already see a few billionaires with many children, such as Elon Musk.

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The whole point of this post is to enumerate HOW things might change. I don't see how vat-growing or warp drives changes the fertility situation. Robots and all dead are listed scenarios.

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Aug 24, 2023·edited Aug 24, 2023

Well, if people are vat grown organisms the size of mice, fertility and population is at the discretion of whoever commands the vats, maturity might be reached much sooner, and Earth could support a population of perhaps hundreds of billions.

If people are colonizing the galaxy with warp drives, their living situations and culture would be very different from today, and different colonists could develop in wildly different and unpredictable directions due to isolation. Resource limitations of Earth would also lose relevance.

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The problem is that it takes skilled TIME to raise kids. Whether they are the size of mice or flying away on warp drives doesn't change that.

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There has been no skill in parenting, raising offspring since the factory.

currently whether Keokuk Iowa, or Harare Zimbabwe, all biped under 16 have a video screen in their face.

You specifically had 'time' to interact with your offspring. Human gen. pop. has not, and the availability dwindles moment by moment.

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If they're genetically engineered organisms, their brains could be designed to mature more rapidly.

Having a kid while traveling to or colonizing a distant world is going to be a different affair from having a kid on present Earth. Yes, having to raise them is more or less constant (unless genetic engineering/AI nannies/culture of child labor), however in space there will be different sociological and economic factors at play with unpredictable effects on people's willingness to have children and ability to raise them.

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There is no general population accepted 'ability' to raise children now.

The only procreation involved with space travel is A/GI farming the biped.

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Everyone ignores the obvious fact: by 2050 half of the population will be African (living in Africa, Europe and USA). And by 2100, most of the population will be African and African hybrid. And when Africans take over all countries and societies will collapse back into primitive conditions at best, but probably more chaotic like today's Somalia.

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Evolution will just replace one set of genes (those that don't value having children) with another (those that do) as you have pointed out before Robin. The timeframe that this will happen over depends on the exact heritability of the preference for more children, but any heritability at all is enough to make this happen on a fairly short time horizon. See for example this paper (https://www.sciencedirect.com/science/article/abs/pii/S1090513817302799). The outcome in the short term will be a much more religious and conservative world as Hutterites, Mormons, Orthodox Jewish people, and religious Catholics and Christians become a larger portion of the population (see for example Shall the Religious Inherit the Earth https://www.amazon.com/Shall-Religious-Inherit-Earth-Twenty-First/dp/1846681448). In the longer term it is likely that offspring of extremely productive people that also value children like Elon Mush will come to dominate as they will be able to outcompete others. But this is less certain because the people being outcompeted may have enough power to band together to stop it. I guess the biggest irony is that people like Elon are worried about a declining population when its genes like his that will prevent this from happening to any appreciable degree.

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I think in the USA Mormons are now below replacement.

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what sense does any of this make in a future with 2.7 C warmer global temperature?

we have 1000 times too many people anyway. "declining fertility" should be renamed "lessening desperation of the overpopulation crisis".

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Averages don't work well in demography. If some small subpopulations have higher birth rates they'll be obscured by the averages but dominant in the long run -- the largest eigenvalue determines the long run behavior. Expect the US to become Hutterites and Orthodox Jews. I don't know who the corresponding groups are in the rest of the world.

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Uh, the way that natural selection works is that the strain of humans who want no children will go extinct and the strain of humans who want children will continue. Whether the wanting is genetic or cultural I don't pretend to know, but a culture can go extinct just as can a genome.

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GPT-4 generated:

Certainly, Mike. Continuing to channel Peter Zeihan's perspective, here's a unique scenario that might align with his thinking:

Helix: 2023-08-24: [Peter Zeihan's Perspective]

Scenario: Geopolitical Realignment and Demographic Partnerships

In a world where fertility rates continue to decline, particularly in developed nations, a new form of geopolitical realignment emerges. Countries facing severe demographic challenges begin to form strategic partnerships with nations that have younger, growing populations.

Demographic Partnerships: Developed nations with aging populations and low fertility rates enter into agreements with developing countries that have youthful demographics. These partnerships involve facilitated migration, education, and employment opportunities, creating a symbiotic relationship where both nations benefit.

Economic Integration: The agreements extend beyond mere labor exchange and encompass economic integration, technology transfer, and investment in infrastructure. The developed nations gain access to a young and vibrant workforce, while the developing countries receive investment, technology, and expertise to boost their economies.

Cultural Fusion: This scenario leads to a unique cultural fusion, where traditional barriers break down, and new hybrid cultures emerge. The blending of different traditions, values, and lifestyles creates a dynamic and innovative environment that fosters creativity and progress.

Strategic Alliances: These demographic partnerships evolve into strategic alliances that reshape the global geopolitical landscape. New blocs form based on demographic compatibility rather than traditional political or economic alignments. These alliances lead to a reconfiguration of global power dynamics, with new leaders and influencers emerging on the world stage.

Ethical Considerations: The scenario also raises ethical questions about sovereignty, identity, and the potential commodification of human capital. The agreements must be crafted with care to ensure that they are mutually beneficial and respectful of individual rights and cultural integrity.

In conclusion, this scenario of geopolitical realignment and demographic partnerships offers a novel approach to addressing the challenges of declining fertility rates. It recognizes the interconnectedness of demographics, economy, culture, and geopolitics and presents a vision of a future where nations collaborate in innovative ways to overcome shared challenges. It reflects a world that adapts to demographic realities by forging new paths of cooperation and integration, reshaping the global order in the process.

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This post is about the world as a whole. Immigration isn't a solution there.

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More GPT-4 (I could never come up with anything like this, hope it is useful):

Acknowledging Robin's focus on global solutions without relying on immigration, here's another unique scenario from Peter Zeihan's perspective:

Helix: 2023-08-24: [Peter Zeihan's Perspective]

Scenario: Global Demographic Marketplaces

In a future where fertility rates continue to fluctuate and vary across regions, a new global system emerges that leverages the power of market dynamics to address demographic imbalances. This scenario envisions a world where fertility becomes a key economic indicator, and nations actively engage in demographic marketplaces to stabilize population trends.

Fertility Incentives: Governments around the world implement a wide range of incentives to encourage higher fertility rates. These incentives are tailored to local cultures and economies and may include financial rewards, tax breaks, extended parental leave, and support for child-rearing.

Global Collaboration: Nations collaborate to share best practices, technologies, and policies that have proven effective in boosting fertility rates. This global collaboration leads to a more unified approach to addressing demographic challenges without relying on migration between countries.

Demographic Investment Funds: International organizations and private investors create demographic investment funds that support projects aimed at enhancing fertility rates. These funds invest in education, healthcare, family support, and other areas that directly impact fertility.

Cultural Evolution: A global movement emerges that prioritizes family and community values, leading to a cultural shift that encourages larger families. This movement transcends national boundaries and becomes a unifying force that helps reverse declining fertility trends.

Technological Innovation: A surge in technological innovation focuses on enhancing fertility and supporting family life. This includes advancements in reproductive medicine, childcare technology, flexible work arrangements, and virtual education platforms that make family planning and child-rearing more accessible and appealing.

Ethical Oversight: The global community establishes ethical guidelines and oversight mechanisms to ensure that the pursuit of higher fertility rates respects individual choices and avoids coercive practices. Transparency, consent, and cultural sensitivity become central principles in this global effort.

Economic Resilience: By addressing fertility rates through a combination of incentives, collaboration, investment, cultural evolution, and technology, the world builds a more resilient global economy. The stabilization of population trends contributes to sustainable growth, innovation, and social cohesion.

In conclusion, this scenario of Global Demographic Marketplaces presents a vision of a world that actively engages with fertility as a global challenge. It recognizes the interconnectedness of demographics, economy, culture, and ethics and offers a comprehensive approach that transcends national boundaries. By leveraging market dynamics and global collaboration, this scenario provides a path toward a more balanced and resilient future, where fertility trends are addressed through innovation, cooperation, and shared values. It reflects a world that adapts to demographic realities by embracing a collective responsibility to nurture and sustain human life.

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"These partnerships involve facilitated migration, education, and employment opportunities, creating a symbiotic relationship where both nations benefit."

We call that auction, or chattel sales.

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Your nine scenarios all seem to assume that culture determines reproductive behavior. I doubt that.

As I learned it and believe it, families get smaller when they get comfortably rich. People who can't keep themselves out of poverty breed like mad in the hope that the kids can support them in old age (a function substituted by social security in rich countries).

Therefore I predict that the coming Great Reset, which is intended to and will impoverish most of us, will result in a massive population explosion. In trying to prevent Malthus from being right, the green movement will have made him exactly right.

From there, we can expect Armageddon within a century from now.

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People don't have kids as a form of social security, people have always had kids for the same reason other species of animals (where the children certainly don't support retired parents) do. https://www.econlib.org/archives/2009/10/was_having_kids.html

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Synonyms for Century can be, millennium or epoch.

Lets go with epoch. 'distinctive period'

Distinctively I am going with -18yrs, less.

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Check out this article on how to increase fertility by increasing the wealth and status of young men.

https://open.substack.com/pub/aporiamagazine/p/the-baby-boom

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I know I'm late to the party on this, but I'd like to suggest what might work either as a new number, or as an addendum to 13: A Different Kind of Gender Equality.

Instead of our current system of gender equality, where both parents equally try to juggle kids and career, we go back to having one parent focus more on the kids and putting their career on the back burner while the other works. The difference is that instead of it always being the woman that does it, parents choose based on their individual circumstances. This means we don't need to go back on feminist values, because the man is equally likely to be the one that stays home.

It works for me. I'm male, and I work part time and take over more childcare duties. It's an absolute delight, I don't see why more men don't do this. I can't think of any stupid office-drone career that equals the joy I get from playing with my daughter. I know some men would find doing this emasculating, but they are all morons. The solution to any feeling of emasculation they have is to stop being morons.

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A potential scenario to consider/add would be a change of norms to grandparents raising their grandkids being the default.

Before industrial capitalism, having children young wouldn't have impacted your career because people didn't have 'careers' like today involving many years of education plus a portfolio of different jobs slowly building career capital. Plus changing lifestyle norms mean you don't want to settle down at 20, but rather keep exploring until your mid 30s-40s.

One way to address this is a change in parenting norms so it becomes the default that grandparents raise their grandkids and kids are had young.

So a typical person would have children at around 20, with the knowledge that they wouldn't be raising them so it would not impact them. These kids would be raised by their 40(ish) year old parents, who wouldn't have raised their kid (that they had in their early 20s). These 40 year old parental-grandparents would have developed the education, career capital and had time to explore and 'get to know themselves' and would by this point be ready to have kids and provide a stable home.

This effectively squares the circle of the divergence between preferences for delaying childbirth into ones 40s and the human fertility window which may be closed by then.

the tricky part would be managing the shift, it would be a huge cultural change.

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Sep 8, 2023·edited Sep 8, 2023

If high desire for more children apart from a culture that pushes in that direction and apart from the desire for sex, is in anyway transmitable from parent to child it should turn around at some point but I agree with the insular groups idea. Like a genetic desire for children gets stronger. Fertility was once controlled by the desire for sex rather than the desire to have children but it could be that some people have a stronger genetically controlled desire to have children.

Groups like the Amish, Laestadian Lutherans and orthodox Jews will become larger parts of the population.

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I’m a bit shocked that the equivalent of the elephant in the room is not even whispered of herein. Are folks seriously concerned that human fertility rates will be what dooms us?? Maybe ya’all need to spend some time in the real world??

“The implications of energy inequality for climate change policy

The study projects energy use through mid-century and finds that, without energy efficiency improvements, “energy footprints would double by 2030, and more than triple by 2050, with half of the increase occurring in India and China.” With rising incomes, more spending will shift from basic goods to luxury goods, especially transport, which at least at the moment is primarily powered by fossil fuels. And that could be a disaster for the climate.”

https://www.vox.com/platform/amp/energy-and-environment/2020/3/20/21184814/climate-change-energy-income-inequality

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Solar, wind, geothermal and nuclear fission together can provide plenty of energy.

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I've put some related prediction markets on manifold into a group, here: https://manifold.markets/group/human-population-crisis

Some of them partially overlap with the list above. There is still some work to be done to create markets for some of the remaining ideas.

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