The usual ideal population preferred by people is quite small. If society is still to have airplanes, trains, electricity, government, etc., though, then the population would probably have to be moderately sized at least.
I would say around 2 billion; 1930ish. Unless we want to go more primitive and then I would say 300,000,000 or so.
2 - 4 billion. Although, TBH, the Earth has enough resources - space, food, etc - to have an even greater population living in relative comfort. The current crisis is more about poverty and unequal distribution than it is about the planet reaching full capacity.
Around 100 million to 500 million.
It’s enough to keep civilization going, at a pleasant, non-aggressive level. It turns the global economy into a “market village” model.
It does cause a slow-down in some kinds of technological research – but among those kinds is weapons research, and I’m fine with that getting sidelined.
But also, the earth may be comfortably supporting those people who are getting their share of the distribution, BUT we are depleting the earth’s stores of many kinds of resources faster than those resources can be regenerated. So the current population (let alone increased populations in the future) may not be indefinitely sustainable.
We need some lesser population, in order to be indefinitely sustainable.
The more the merrier. I do agree world population growth needs to be slowed down in the short run and that many in the First World (especially the United States) will need to downsize their standards of living but some people here are really pessimisstic about the potential of technology to continually increase the maximum world population capacity.
Some people here sure hate humanity.
Why would anyone “want to go more primitive”?
Also drastically reduced industrial capacity, cultural activity etc.
Any harm caused by advanced weapons technology (which is disputable since most of the great innovations in warfare have reduced casualties-ie mechanized warfare eliminating the bloodiness of trench warfare or nuclear weapons ending great power warfare) have been far exceeded by the benefits brought by technological advancements in all other fields.
Some of us are realists. The world is already greatly overpopulated as evidenced from everything from global warming, large-scale species extinction, fresh water issues to farm land erosion. We can sustain higher populations in the short-term (decades to a couple of centuries at best). In fact, we have to because we are about to add about 2 billion more people in this century alone which is more people than existed in the whole world a little over 100 years ago and overpopulation was a problem even then in hindsight but people want to treat the same number like a rounding error now because we are so far past the sustainable point.
However, the only reason that is possible at all is because we are quickly burning through every form of non-renewable resources there are to make that possible. There is nothing good or responsible about that. In the end, it isn’t even a choice. Nature will win and kill off billions of people and other invasive species that we caused just as readily as we kill fleas on a dog.
Everything I have read suggests, that if you take all current and anticipated technology improvements and smooth out wealth distribution, you could have an indefinitely sustainable human population of 1 - 2 billion people. Anything much higher requires unsustainable resources and limits the time to collapse to anywhere between the end of this century to a few hundred years from now. Again, that means the devastation of every human society, starvation and extreme warfare brought on for competition for resources that simply can’t support everyone.
There is nothing humanitarian about ‘the more the merrier’ viewpoint.
Why would a population of 1/10 or 1/20 of our current population reduce cultural activity? Has there really been a meaningful increase in cultural activity – specifically in diversity, as opposed to mere numbers – in correlation to the growth of the world’s population?
Cultural activity is better correlated to wealth and comfort. People who aren’t starving are more likely to paint, sing, weave, write, act in plays, and so on. A smaller, wealthier population would be a huge boon for cultural expression.
I definitely agree that industrial production would be reduced, but that could lead to the abandonment of the current “planned obsolescence” model and toward a wiser industrial philosophy.
100 billion sounds like a good number. Still plenty of room for nature, while having far more technological, industrial, and cultural capacity.
Obviously we can’t do it the way we’re handling the current state of affairs. We’ll need a wholesale switch to sustainable industry. Hopefully, some of that industry will be off-planet. Even if we can’t import material resources, we can at least import energy.
A trillion people would probably be a bit much. We don’t want to live on Trantor or Coruscant. I guess we’ll want off-world colonies eventually.
I voted “between 1 and 4 billion”, but this means 1 billion for me.
We don’t need multiples of billions of people to sustain anything like culture or industry - automation has meant most anything productive needs a lot less people to do it than in the past.
Probably about 160. That would be 150 to form our own Dunbar’s Number tribe, and 10 people for us to pick on.
Any of the people I do Living History with, a majority of the Amish – lots of different people. Turn back the clock to say 1750 or earlier? I could manage that.
Many folks favor a headcount of 1% to 10% of current.
I wonder what they think of the process whereby we select and eliminate 90 to 99% of the current population. Or slower, but almost equivalently, require 90 to 99% of the current population to not reproduce. By force if necessary, and it will be necessary.
These discussions can be entertaining, but I take it as given we can’t get there from here. So it becomes a fantasy discussion, just like the ones about unicorns, cubical Earths, and totally honest and emotion-free politics.
Presumably you’re a man! As a woman I would never want to turn the clock back. This is the first era where women (at least in the Western world) really have control of their reproductive lives, and as such, are not tied to having pregnancies or avoiding pregnancy.
That being said, we do have way too many people. I’d say 2 to 4 billion, but really getting the world population down to 1 billion would be sufficient.
Well. I am doing my part to get there already - having no children!
Right about a billion, and…this is important…I am one of those people.
I’m going to miss some of you.
But what if you need, say, heart surgery someday? Where’s the technology?
This thread isn’t about genocide or eugenics, it’s just a simple opinion poll. You don’t have to explain how to get to the desired number, just what the desired number would be.
You mean it’s not time to start culling the herd? 
2 (me and Kate Upton)