What'll the world population be in 2100?

[VetLegion]

You expect the population of ths USA to grow by 600% in the next 94 years?

Yeah. Stop posting and start working on it!

[Sandman]

Originally posted by DanS
The demographers haven't been good predictors in the past with regard to population growth, so I don't put much stock in what they say. Really, the population is still to be determined. There could be baby booms and the like.

Where'd you get this from?

2100 is a very long time away - it will probably be more different from 2006 than 2006 is from 1912. Widespread clinical immortality could throw all predictions out of the window.

[KrazyHorse]

7-10 billion

Probably on the low side of that

8, maybe?

[KrazyHorse]

Significant upside risk on that, though...

[Kidlicious]

Zero

HOUSE OF YAHWEH®

[Q Classic]

<100 million, but that's just because I plan on lobbing a few Planet Busters here and there to clean the planet of the... riff-raff. Y'know, the undesireables.

[Jon Miller]

Maybe a few hiding in caves..

JM

[lord of the mark]

Originally posted by KrazyHorse
Significant upside risk on that, though...

Look at TFRs and population growth rate declines in countries like Iran, Morocco, China. Hong Kong and Singapore have estimated TFRs close to one, which is amazing. It increasingly appears that the tendency of the demographic transition to take TFRs below replacement levels is not limited to Southern and Eastern Europe - they just got their first. This is one of the more striking empirical facts of social science today, and I dont think the UN midlevel estimate of 9 billion really takes it into account.

[KrazyHorse]

I'm not estimating 9 billion. I'm estimating around 8

But while I feel that this is the best guess, my feeling is that there is more chance of it going significantly above 8 billion than below it.

Could it be 6? Yes, but I think it's likelier to be 10 than 6

[DanS]

Originally posted by Sandman
Where'd you get this from?

What do you mean by that? During the 70s and 80s, all the talk was of a population explosion rather than a moderation of population growth, as has occured.

2100 is a very long time away - it will probably be more different from 2006 than 2006 is from 1912. Widespread clinical immortality could throw all predictions out of the window.

It could. Who knows. Even the steady increase in life expectancy (0.3 years/year in the US) could moderate or increase substantially due to both unforeseen and misjudged factors.

[lord of the mark]

Originally posted by KrazyHorse
I'm not estimating 9 billion. I'm estimating around 8

But while I feel that this is the best guess, my feeling is that there is more chance of it going significantly above 8 billion than below it.

Could it be 6? Yes, but I think it's likelier to be 10 than 6

At some point the slowdown and reversal in population growth in China and India, combined with their continued development, is going to dramatically impact the market clearing price of unskilled labor. At that point even the worst African hellholes become desirable places for manufacturing. At which point even the high African TFRs are likely to decline.

Morocco has a rapidly declining TFR. Mali and Niger do not. Is there really something in the culture of Mali and Niger that makes them more resistant to modernization than Morocco? I dont think so. The demand for labor simply hasnt reached the point where it can overcome the geographic and institutional barriers. Someday it will, and given current trends, its probably not that far off.

here are figures for Morocco, BTW

http://www.prb.org/Template.cfm?Section=PRB&template=/ContentManagement/ContentDisplay.cfm&ContentID=13802

to relate this to the big numbers

UN projection is global pop tops out at 9 billion in 2075, I think. Now OP asked about 2100. Assuming the UN projection for 2075 is right, the 2100 pop is likely to be lower, since we have far more examples of TFRs continuning to decline after hitting replacement, than of stabilizing at or near replacement. A pop in 2100 of 8 billion or less would be indicated. But I think the pop is likely to top out earlier, and lower. Say at 8 billion in 2060. In whicih case you now have 40 years of likely decline, and from a lower peak. 6 billion seems the LIKELY case, which at least as much possibility it will be LOWER than that, as that it will be as high as 9 billion.

[lord of the mark]

Originally posted by DanS


What do you mean by that? During the 70s and 80s, all the talk was of a population explosion rather than a moderation of population growth, as has occured.

It could. Who knows.

Even then people who knew better were talking "demographic transition" at the Paul Ehrlich types. They just didnt expect the DT to spread quite as fast as it has.

[KrazyHorse]

My guess as to prob. dist. of world pop. circa 2100

[KrazyHorse]

(bump at left is all-out nuclear war/superdisease/asteroid strike)

[lord of the mark]

I think you seriously underestimate the probablity of the goldilocks scenario - neither catastrophic disease/war nor overpop, but the world following an accelerated demo transition involving high wage levels, high rates of female education and work force participation, and very low TFRs. Id say a pop of 3 billion in a goldilocks scen is at least as likely as a global war-disease catastrophe, and probably more likely than a pop of 12 billion from a revived pop bomb.