
The Lancet: World population projections by 2100 - wslin
https://www.thelancet.com/article/S0140-6736(20)30677-2/fulltext
======
vmurthy
For me this stood out: "The reference projections for the five largest
countries in 2100 were India (1·09 billion [0·72–1·71], Nigeria (791 million
[594–1056]), China (732 million [456–1499]), the USA (336 million [248–456]),
and Pakistan (248 million [151–427])."

The big surprise being China,of-course. A drastic _decrease_ projected in the
coming 80 years.Should have policy consequences as well, I would think.

~~~
Someone
China’s predicted population decrease is a logical consequence of its one
child policy ([https://en.wikipedia.org/wiki/One-
child_policy](https://en.wikipedia.org/wiki/One-child_policy))

If you compare
[https://www.populationpyramid.net/china/1980/](https://www.populationpyramid.net/china/1980/)
with
[https://www.populationpyramid.net/china/2020/](https://www.populationpyramid.net/china/2020/),
you see how drastic its effect on China’s population pyramid was. Drastically
fewer kids means fewer parents 20-30 years later.

(There also is a bit of an effect of richer people having fewer children, but
for China, that effect is relatively small)

~~~
shalmanese
Population Pyramid estimates the 2100 population of China to be 1.06B which is
45% higher than the 732M figure estimated by Lancet.

1B feels like a lot more realistic estimate than 750M.

~~~
vmurthy
The most interesting thing for me in this report coming out is that
societies/governments taking note of this might incentivise outcomes. E.g., if
China thinks that 750M is too low keeping its longer term interests, it might
tweak the 1-child policy or encourage immigration etc by 2050.

------
Aerroon
I find these predictions fascinating to think about. Did we get them right
this time? I remember that we were taught about the idea of overpopulation in
school. As I understand, it was believed in the 60s and 70s that the world
population would keep massively increasing. People were worried about
overpopulation. At this point we know that that's not true - it seems that
essentially all rich countries see a decline in birthrates. They might
increase in population, but it happens due to immigration. However, will this
pattern hold?

As I understand it, before the industrial revolution, the population was
what's described as Malthusian. As a country became richer it tended to have a
population increase, which meant that an estimate of GDP per capita remained
relatively similar. Over thousands of years you'd see maybe a doubling or
quadrupling of it. Ie the median person in the year 500 AD lived rather
similarly to the median person in the year 1500 AD.

When the industrial revolution rolled around, things changed. The estimate of
GDP per capita increased faster than the population. People became richer and
their lives became significantly better. This came with a substantial
population increase, because people started living longer. The fruits of
progress spread to poorer areas. The increase in food availability and
medicine made many population counts skyrocket.

At some point during this it turned out that the richest areas started seeing
a significant decrease in birthrates though. Why? I'm unsure. Perhaps people
wanted better lives for their children and they couldn't afford to have as
many children? Perhaps it wasn't necessary to have as many children anymore
(social security)? Regardless what the reason is, birthrates have declined in
developed countries. This allows us to plot a peak for the human population
and decline afterwards. We don't need to worry about overpopulation anymore.

Will this pattern hold though? What if it turns out that when a society hits a
GDP per capita of $500k of today's money that the birthrates start increasing
again? 3% growth of GDP per capita plotted over 80 years would put US GDP per
capita at $668k. What's the chance that there is no societal break point in
the future that reverses the birthrate decline? Quite a few countries seem to
be actively working on trying to find something like that.

~~~
X6S1x6Okd1st
Female empowerment is what is listed in the paper and what is generally
accepted.

I've typically heard two drivers:

1) children turned from an economic boon/necessity to a sink. They can start
helping with farm work pretty early, not quite so much when the industry work,
they have to be somewhat older and can't tag along when the parents are
working.

2) women could spend their time working and earning money. They could start to
support themselves.

We've been able to accelerate this trend by offering access to contraception
and decreasing infant mortality.

~~~
Zenbit_UX
Not just empowerment but education. The higher educated a woman is the more
TFR goes down.

------
jacquesm
These studies are fascinating but I think they should stay away from such
detailed predictions as 'in the reference scenario, the USA was forecasted to
once again become the largest economy in 2098'. That's just way too far out to
make any meaningful statements about a simple ordering of economies in
relative size.

~~~
cj
Is that really a prediction in the study? Or does their reference scenario use
that (unknowable assumption) as a necessary input in calculating their
population predictions?

------
throw0101a
There's a good (though hour-long) presentation by the late Hans Rosling call
"DON'T PANIC — Hans Rosling showing the facts about population":

* [https://www.youtube.com/watch?v=FACK2knC08E](https://www.youtube.com/watch?v=FACK2knC08E)

"Don’t Panic – The Facts About Population":

* [https://www.gapminder.org/videos/dont-panic-the-facts-about-...](https://www.gapminder.org/videos/dont-panic-the-facts-about-population/)

------
yodsanklai
Do they take into account the consequences of global warming?

~~~
nl
To some degree. They note that they don't have accurate enough predictions to
calculate changes to net migration due to climate change.

------
hartator
Isn’t the Lancet the publication who promoted that obviously bogus COVID study
then retracted it without an apology? Why should we trust them again?

~~~
yosito
Yeah the Lancet has had some questionable publishing standards as of late, but
the thing about science is that you should always hold everything loosely, run
more experiments, try to disprove pást studies' findings, and take everything
with a grain of salt until it's confirmed by several peer reviewed studies.
So, we shouldn't trust the Lancet, and we don't need to, because everything in
proper science should always be taken with a grain of salt.

------
ggm
It stands out that a worldwide event like coved won't alter the trajectory as
far as I an see, on these trends. If i missed something long lasting on the
natural reproductive rates of these economies id love to know.

Whats strongly causative of the decline is literacy, especially women's
literacy, and women's body autonomy and reproductive rights.

US opposition to WHO and to funding contraception and abortion is (thankfully)
being counterbalanced by the gates foundations work, and other funding
sources. A pox on the religious right, and American foreign policy.

~~~
feralimal
> It stands out that a worldwide event like coved won't alter the trajectory
> as far as I an see, on these trends. If i missed something long lasting on
> the natural reproductive rates of these economies id love to know.

And that's a good thing, right?

~~~
ggm
It would be horrid if covid was visibly altering a long term trend even if it
was net beneficial.

~~~
iso1210
If covid leads to a long term increase in remote work that itself could lead
to a change in demographics as people reduce moving to cities and away from
family support networks, which could impact on fertility rates.

------
albertTJames
"Approximately correct projection of world population by 2100, given that
nothing horrible happens by then."

------
wslin
This study came out in 2020-07-14.

Link to the study can be found on the webpage.

~~~
vmurthy
PDF of the same :
[https://www.thelancet.com/action/showPdf?pii=S0140-6736%2820...](https://www.thelancet.com/action/showPdf?pii=S0140-6736%2820%2930677-2)

------
AniseAbyss
I refuse to believe that the only way for economic growth is population
growth. Thats not sustainable. More investment in replacing the workforce with
automation.

~~~
spodek
It's not. People used to believe we couldn't go to the moon. They just didn't
see other models, or benefited from old models.

Even more than economic growth is growth in standard of living, quality of
life, health, and other things that population growth is now causing to
decline, however much it helped before. Plenty of human populations have lived
peacefully, stably, and abundantly without economic growth. Plenty have grown
to overshoot and collapse.

In Thailand, for example, Mechai Viravaidya helped lead a nation go from 7
children per woman to below replacement level. Think the opposite of the One
Child policy -- instead of forced abortions and sterilizations, all voluntary,
fun teaching kids about condoms and making them available everywhere. It
increased stability, peace, and abundance. Here's his TED talk:
[https://www.ted.com/talks/mechai_viravaidya_how_mr_condom_ma...](https://www.ted.com/talks/mechai_viravaidya_how_mr_condom_made_thailand_a_better_place_for_life_and_love)
"Thailand's 'Mr. Condom,' Mechai Viravaidya, retells the country's bold plan
to raise its standard of living, starting in the 1970s. First step: population
control. And that means a lot of frank, funny -- and very effective -- talk
about condoms."

------
godmode2019
"The global population was projected to peak in 2064 at 9·73 billion
(8·84–10·9) people and decline to 8·79 billion (6·83–11·8) in 2100."

Baseline of 9.73 billion.

"China was forecasted to become the largest economy by 2035 but in the
reference scenario, the USA was forecasted to once again become the largest
economy in 2098"

That sounds like they they forecast war?

Also

"meeting the Sustainable Development Goals targets for education and
contraceptive met need would result in a global population of 6·29 billion
(4·82–8·73) in 2100"

Is the 2.4 billion people missing people a form of genocide or just good
heath?

"Funding Bill & Melinda Gates Foundation."

~~~
wslin
They explained their methodology on forecasting these populations by factors
such as birth rates, migration, and mortality rates. Where did you read the
part that mentioned wars?

------
aaron695
The Gates foundation has a interest in keeping estimates of the population
down low.

It's important to help promote global community now, today when it matters.

And given how rich countries progress, extrapolation to poor countries make
sense.

But it's not how it will go down, look at attempts 80 year ago what they
thought 2020 would be

Not a great example, but it's well under -

[https://www.ssa.gov/oact/NOTES/pdf_studies/study033.pdf](https://www.ssa.gov/oact/NOTES/pdf_studies/study033.pdf)

There are massive changes coming, and they won't be in the negative direction.

Longevity will mean increased fertility.

UBI means things other than money will matter, like it or not when jobs start
decreasing.

~~~
nl
> The Gates foundation has a interest in keeping estimates of the population
> down low.

The paper says:

 _Role of the funding source The funders had no role in study design, data
collection, data analysis, data interpretation, or writing of the report. All
authors had full access to all the data in the study and had final
responsibility for the decision to submit for publication._

> But it's not how it will go down, look at attempts 80 year ago what they
> thought 2020 would be

> Not a great example, but it's well under -

>
> [https://www.ssa.gov/oact/NOTES/pdf_studies/study033.pdf](https://www.ssa.gov/oact/NOTES/pdf_studies/study033.pdf)

They estimated 2025 US population to be between 225M and 392M depending on the
projection methodology used. The current population of the US is 328M, so this
seems pretty good for an estimate 70 years ago!

> Longevity will mean increased fertility.

This would seem a bold claim. It hasn't anywhere in the world so far, and the
correlation between increased longevity and decreased birthrates is _very_
strong.

~~~
aaron695
> The funders had no role in study design,

The Funders know how it'll come out.

Studies don't take into account the leaps that will happen because we don't
know what they are. Things don't just continue as the previous 80 years. These
jumps happened even when we didn't have the internet to super charge stuff.

> 2025 US population to be between 225M and 392M

That's 2050 in the document.

2020 is 210 - 305 million estimate. (pdf p29)

> decreased birthrates is very strong.

But not fertility. You won't be living to 120 without being a healthy and
fertile 60 year old. It's fun to have work as number one for 20 years, but if
it's easy to have kids in your 40's without IVF things will change.

~~~
nl
>> 2025 US population to be between 225M and 392M

> That's 2050 in the document.

Yes, you are right, my apologies.

2025 predictions are between 221M and 318M (table, page 16) which makes their
"projection B" scenario almost exactly correct.

>2020 is 210 - 305 million estimate. (pdf p29)

Page 29 is a table called "Relative comparison of dependant and productive
groups in the United States". There are no population numbers.

Page 25 has a graph which you maybe referring to. That doesn't have numbers,
but they seem to be plotting the numbers from page 16.

> But not fertility. You won't be living to 120 without being a healthy and
> fertile 60 year old.

What evidence do you have of that? Increased life expectancy for women so far
hasn't been matched by an increase in fertility beyond 40 years old.

~~~
aaron695
> Increased life expectancy for women so far hasn't been matched by an
> increase in fertility beyond 40 years old.

You've said this with some certainty, were are you getting this from? This
doesn't fit with all current data about general health and longevity, so I'd
like to see who's saying this and what their case is.

~~~
nl
The ovarian reserve doesn't somehow increase with increased longevity. The
chart from Wikipedia is as good as anything on this:
[https://en.wikipedia.org/wiki/Ovarian_reserve#/media/File:Wa...](https://en.wikipedia.org/wiki/Ovarian_reserve#/media/File:WallaceKelseyModel.jpg)

The ovarian reserve only decreases from birth, so it becomes less and less
likely for a woman to conceive as they get older.

[https://en.wikipedia.org/wiki/Age_and_female_fertility](https://en.wikipedia.org/wiki/Age_and_female_fertility)
also notes: _A review in 2012 came to the result that therapeutic
interventions to halt or reverse the process of reproductive ageing in women
is limited, despite recent reports of the potential existence of stem cells
which may be used to restore the ovarian reserve_

[https://en.wikipedia.org/wiki/Advanced_maternal_age](https://en.wikipedia.org/wiki/Advanced_maternal_age)
has some further good reading on this.

