[hamdani yusuf]

Many people think that having kids are a form of investment. They take extra effort now for future benefits. They take care of their kids hoping for payback when they are old.
Others just follow their sexual instinct without thinking any further.

[hamdani yusuf]

https://www.wsj.com/articles/u-s-population-growth-slows-birth-rate-decline-economic-risk-11627231536?ns=prod/accounts-wsj

America’s weak population growth, already held back by a decadelong fertility slump, is dropping closer to zero because of the Covid-19 pandemic.

In half of all states last year, more people died than were born, up from five states in 2019. Early estimates show the total U.S. population grew 0.35% for the year ended July 1, 2020, the lowest ever documented, and growth is expected to remain near flat this year.

Some demographers cite an outside chance the population could shrink for the first time on record. Population growth is an important influence on the size of the labor market and a country’s fiscal and economic strength.

How many people is necessary to sustain advancement in science and technology?
If the population of ancient Egyptians were only 1000, was it possible to build the great pyramid?
With current number of people, is it possible to build a multiplanetary society?

[alancalverd]

Pay women not to have babies. Then wait. The passage of time is very effective at culling the population, with no human intervention required.

How much?
For how long?

My model pays £500 every 6 months from age 14 to 60 if you are not pregnant. You get one "bye", so each woman can have one child without losing her benefit. There are no child benefits, grants, maternity leave, etc. but health and education services remain free. So having a child is a serious and significant financial decision.  In terms of the UK economy this costs the state less than a second or any subsequent child.

I've projected the model for about 100 years, by which time the UK population will have decreased to an indefinitely sustainable level (about 5,000,000) with a significantly better quality of life than we have now, and the "bye" can be raised to 2 children.

[alancalverd]

Many people think that having kids are a form of investment. They take extra effort now for future benefits. They take care of their kids hoping for payback when they are old.

Experience will show that they are wrong, at least in the UK.

Others just follow their sexual instinct without thinking any further.

The instinct is to copulate at every available opportunity. We have already learned not to do that.

[alancalverd]

How many people is necessary to sustain advancement in science and technology?

One Einstein per generation.

If the population of ancient Egyptians were only 1000, was it possible to build the great pyramid?

would it have been necessary?

With current number of people, is it possible to build a multiplanetary society?

You just need to seed the new planet with one pregnant human. But if we reduce the earth's human population to a sustainable level, there would be no need to look elsewhere and every reason not to.

The best way to solve any problem is to eliminate it, and if you can do so by doing nothing (i.e not  making babies), you have found the most intelligent solution of all.

[hamdani yusuf]

The instinct is to copulate at every available opportunity. We have already learned not to do that.

Science and technology in the form of contraceptions let us follow the instinct without dealing with its side (or main? depends on perspective) effect.

[hamdani yusuf]

How many people is necessary to sustain advancement in science and technology?

One Einstein per generation.

If the population of ancient Egyptians were only 1000, was it possible to build the great pyramid?

would it have been necessary?

With current number of people, is it possible to build a multiplanetary society?

You just need to seed the new planet with one pregnant human. But if we reduce the earth's human population to a sustainable level, there would be no need to look elsewhere and every reason not to.

The best way to solve any problem is to eliminate it, and if you can do so by doing nothing (i.e not  making babies), you have found the most intelligent solution of all.

Just googled for minimum sustainable population.

They created the “50/500” rule, which suggested that a minimum population size of 50 was necessary to combat inbreeding and a minimum of 500 individuals was needed to reduce genetic drift.

https://en.wikipedia.org/wiki/Minimum_viable_population

Minimum viable population (MVP) is a lower bound on the population of a species, such that it can survive in the wild. This term is commonly used in the fields of biology, ecology, and conservation biology. MVP refers to the smallest possible size at which a biological population can exist without facing extinction from natural disasters or demographic, environmental, or genetic stochasticity.[1] The term "population" is defined as a group of interbreeding individuals in similar geographic area that undergo negligible gene flow with other groups of the species.[2] Typically, MVP is used to refer to a wild population, but can also be used for ex-situ conservation (Zoo populations).

[acsinuk (OP)]

To reduce the risk of overpopulation needs a system of education that makes our teenage children understand the consequences to the planet of overproduction and how it causes poverty.  They must be taught that 2 is enough if the family is to enjoy a high standard of living.
Government could try large tax reductions for women who have less than 3 children but really its about understanding that climate change is caused by overpopulation and not just CO2 emissions.

[Bored chemist]

They must be taught that 2 is enough if the family is to enjoy a high standard of living.

You can not teach them that if it is not true. In many parts of the world, the only security you have in your old age is that your children will look after you.
So having just two would be stupid.

Experience will show that they are wrong, at least in the UK.

Earth calling Alan; most people do not live in the UK (or anywhere much like it).

[alancalverd]

You will find that wherever there are established state education and pension schemes, the young do not support the old: that is done by the 20 - 60 cohort of working taxpayers. Given that the 0 - 20 year-olds are also supported by that group, reducing the 0 - 20 cohort increases the working fraction and thus the available resources for the elderly.

Even in nascent civilisations like the USA, the over-60s are supported by the investments they made in their own working years, not by infant labor.

Alternative means of reducing the population to a sustainable level would be welcome, but one that doesn't involve mass murder, uncontrolled pandemic, starvation, or anyone actually doing anything, seems the most attractive to me.

[hamdani yusuf]

Given that the 0 - 20 year-olds are also supported by that group, reducing the 0 - 20 cohort increases the working fraction and thus the available resources for the elderly.

What would happen the next 20 years?  The work forces would be reduced. The next 40 years would be worse.

[alancalverd]

Not so. My crude model assumed that almost all babies are born to women around age 20 (it's fairly accurate), so the number of fertile women decreases with time and the birth rate thus drops again. The "working fraction" increases steadily from 0.5 to about 0.65 and the per capita natural resource availability increases as the population decreases.

Remember a substantial part of the workforce is employed in cleaning/feeding/educating/policing/repairing the youngest cohort, or paying someone to do it.

[hamdani yusuf]

Not so. My crude model assumed that almost all babies are born to women around age 20 (it's fairly accurate), so the number of fertile women decreases with time and the birth rate thus drops again. The "working fraction" increases steadily from 0.5 to about 0.65 and the per capita natural resource availability increases as the population decreases.

Remember a substantial part of the workforce is employed in cleaning/feeding/educating/policing/repairing the youngest cohort, or paying someone to do it.

It ends up with balancing resources production with consumption. Reducing population reduces both, although not necessarily  to the same extent. That's why more accurate and precise model is important.
There are some options to increase ratio of resources production to consumption. Reducing unproductive population is one of them. Another option is improving production technology. Empowering unproductive population to become more productive or less consumptive, e. g.  by genetic and epigenetic editing, robotic, nanotechnology,  AI.
Expanding humanity beyond earth is another option.

[alancalverd]

Production depletes resources by turning them into products and waste.

Extending the curse of homo sapiens to other planets does not make life on this one any better.

[hamdani yusuf]

Production depletes resources by turning them into products and waste.

Extending the curse of homo sapiens to other planets does not make life on this one any better.

Define better.

[alancalverd]

Having more, cleaner food and water.

[hamdani yusuf]

Having more, cleaner food and water.

Why so?

[alancalverd]

Don't ask me. Ask the starving, diseased millions who have never seen a water tap. They appear fairly regularly on TV.

[hamdani yusuf]

Don't ask me. Ask the starving, diseased millions who have never seen a water tap. They appear fairly regularly on TV.

Why do they want more and cleaner water and food?
Is current condition not good enough?
What can possibly be done to improve it?

[Bored chemist]

Why do they want more and cleaner water and food?
Is current condition not good enough?

Are you being deliberately offensive?