https://www.cambridge.org/core/journals/japanese-journal-of-...
previous discussion: https://news.ycombinator.com/item?id=34486824
I can explain the math, but the result is pretty simple. If we imagine an equilibrium point where everybody has the same fertility rate (the typical case being when the final healthy fertility rate generation dies off - just leaving offspring upon offspring of comparably low fertility rate generations), then at the point your population will start changing by a factor of ~fertility_rate/2 every 20 years. So for Japan, with a current fertility rate of ~1.4, they'll be losing 30% of their population every 20 years, for an annual decline of around 1.5%.
Right now they're only losing about 0.5% per year. So they're still in their glory days relative to what's to come starting around 2060. And that future which they're headed towards is the one most Western economies are also headed towards if we don't fix this problem.
[1] - https://en.wikipedia.org/wiki/File:Japan_Population_Pyramid....
[2] - https://data.worldbank.org/indicator/SP.DYN.TFRT.IN?location...
I assume this "zeitgeist" is among academics?
'Cuz I fear a common political zeitgeist in some countries is a combination: "Overpopulating-Others, Underpopulating-Us."
Japan's TFR fell below replacement around 1973, iirc. So we should wait at least till 2070 before making assertions about the severity or otherwise of the issue. In the mean time, it sure looks serious.
Japan has been propping up its economy with debt. It has the highest public debt to GDP ratio in the world. Is that sustainable if interest rates climb? I don't know.
One can say that Japan's economy was still buoyed by global population growth, export growth, etc.
The rate of decline is important to monitor for the purposes of managing expectations of supply and demand in the markets.
"You want to force women to be baby-making machines", and more vitriolic rhetoric, and loss of tenure, is what happens when someone raises the issue.
I think of this as one of Iain Banks's "Outside Context Problems", something that our society cannot (allow itself to) understand or even see, so it cannot begin to solve it.
The right wing so far hasn’t provided any solutions.
I have one child. I would prefer to have two, but I can’t afford it. For reference: my income is in the top 2% for my country and the top 5% in the affluent part of the largest city. I literally cannot afford to buy a house big enough for a growing family unless my partner also works full time. That’s nuts.
(I think I read about this on the IIASA website.)
Time will tell.
Who benefits?
China and India having 2.5 billion if they are subsistence farming is a much faster different thing that China and India with some approximation of western lifestyles.
Demographic decline does seem endemic to urbanization, but urbanization is hand in hand with western consumption rates.
Net economic activity will probably increase in net, but with, uh, bumps.
But of course you are correct. Urbanization is responsible for the largest population migrations and geographic redistributions of the last century. I consider it the major factor in the demographic birth rate declines.
Take a look at the massive population increase especially in some countries in 50 to 100 years, even ones without huge amounts of land..population density has skyrocketed vs historical norms. It is no wonder that eventually this puts pressure on birth rates, and some of the lowest birth rates are found in places with some of the highest population densities.
Cost of living and real estate has risen, and it will be a good thing for this to reverse or slow. And some foolish leaders want to short circuit this natural correction by importing new people to compete with local citizens for real estate and resources. Not smart. It will only depress domestic birth rates further.
To your point of housing: that is the most clear example of a thing that is artificially constrained by policy. The reason there are housing shortages has absolutely nothing to do with resource constraints and everything to do with terrible policy decisions.
In the United States 75% of the population lives on 2.7% of the total land area. And in the last century we figured out how to harness unlimited energy, produce as much clean drinking water as we could ever need, practically unlimited food production, raised the quality of life for the average human a thousand times over, not even getting into the fact that we are on the cusp of cheap, reusable access to space. I would consider the human population unbounded.
Our aquifers are being permanently drained, our most productive regions are rapidly desertifying, our growing seasons are becoming increasingly unstable as the climate shifts, our crops are genetically homogenous and therefore catastrophically susceptible to disease, our rampant use of pesticides is unraveling the food chain, we're 100% reliant on the use of artificial fertilizers which is dependent on functioning global supply chains and fossil fuels, and even if you can grow the food there's no guarantee that you have the logistics network necessary to distribute it before it rots.
Which is all to say, food is far from a solved problem. And there's nothing in space that's going to address that particular need.
The world is... only partially finite. The resources are not finite. Check studies for oil wells that have replenished in China over 100 year periods.
Finite space is a tacit of conventional wisdom. Cities like old and modern Rome would disagree.
Your view is centered particularly in the past.
Can you send me some of whatever you've been imbibing?
So start at the bottom. And say we have exactly 2 twenty year olds. Since there are 2 twenty year olds there must be 4 forty year olds, 8 sixty year olds, and so on. This generalizes to there being a total of (2^n) people of age (20*n). So there are 512 people of age 180. The entire population is 512 + 256 + 128 + ... 1 = 1023. So what happens when this 180 year old generation dies? Your population declines by half. What happens twenty years later when the 256 population group dies? Your population decreases by half. So each generation, you start seeing an exponential halving of your population.
So how long people live doesn't actually matter. All it does is add some noise/delay as you shift from an equilibrium between fertility rates. And once that equilibrium is reached, your population will shift by a factor of fertility_rate/2 every breeding generation (~20) years. This holds true whether people live for 40 years, or 40,000. So with a fertility rate of e.g. 1 your population will exponentially decline by 50% every 20 years, until you go extinct or start having babies.
Lots fewer babies are dying, a good amount of young adults are staying alive, some middle age people are living longer, and a handful of older folks are too.
But once you get to 80, 90, your life expectancy is within a few years of where it would have been 100 years ago.
There’s absolutely no evidence that medical technology has made any impact on the maximum age humans can live.
And any impact it’s had on the raw numbers making it past 100 are utterly dwarfed by the kind of factors affecting global population. Like tiny, tiny percents of the population are in this “ nouveau old”.
We'll probably have more outliers of wealthy/healthy people living longer, but poor management of broader access to basic health and education may not result in that drastic an increase in overall average results.
However that could have been UK specific data.
*EDIT*: It was global, data comes from the Lancet, which is considered a strong source by many: https://www.thinkglobalhealth.org/article/global-life-expect...
