The difference with the Japan case is that China is going to have a larger base of young, very well educated people than the US for at least the next century unless something changes dramatically with either birth rates or immigration.

China is facing severe demographic issues for the next 20-30 years due to their terribly short sighted one-child policy and their poor immigration rates. Literally the opposite of what you're saying. Where on earth did you get your facts from?

With the population edge they have, they will still have more young people than us. More of their output will have to go for caring for the elderly, but that will scale with technology.

Why does having a large population matter? If you look at the top 10 countries in terms of population (China, India, US, Indonesia, Pakistan, Nigeria, Brazil, Bangladesh, Russia, Mexico), most of those places are not exactly heavyweights on the international scene.

There are so many factors that contribute more to economic and political success than sheer population. I would even say that a large population is a bad thing in many cases. India would be better off with fewer people. Their infrastructure can't handle their density, they don't have enough jobs for their educated workers, there's a lot of sectarianism conflict between various religions and casts, etc.

High population + low GDP per capita is probably the worst situation a country can be in IMO. So it's not enough for China to have a billion people—those people have to be doing something productive for the economy.

Not Zeihan tier demographic analysis which is a start.

PRC currently generating ~5m STEM per year, aka OECD combined, multiple times more than US has ability to train or brain drain. And relatively proven ability to coordinate talent. Project that out next 20-30s from previous 20-30 years of birth rate and PRC on trend to add 50M-100M STEM to workforce, just STEM, not including other skilled workers, which is the greatest high skill demographic divident in recorded history. Literally no country in the world, at any time in the past or projected future has better demographics for actual global competition than PRC in the next 30 years. Including India who will have more people, but have all the issues you noted that will likely prevent them from actually coordinating human capita enmass successfully in the time it takes their youth demographic divident to expire.

Contrary to naive PRC demographic pyramid bomb arguments that doesn't address what you correctly note below - quality of human capita. By 2050, PRC is going to add more STEM talent than US is projected to increase population. All the news of PRC climbing up value chains, leading in science and innovation indexes from last few years? Or moving from 1T to 18T economy. Done by growing STEM from ~2M to ~17M STEM exploited via industrial policy that west is now copying. PRC is moving from workforce with 25% skilled talent to 60/70/80 of modern economies with 60% and increasing tertiary education rate that biases towards science will look weak on per capita stats due to huge existing cohort of old / undereducated, but it absolute terms it's a demographic advantage no country currently has conditions to remotely rival. Then note how net population decline will reduce resource dependency and you basically have the most optimal mix of demographic trend for PRC with respect to geopolitical competition.

Are those demographic issues difficult to govern/manage? Yes, but they're also close to ideal conditions for improving comprehensive national power within PRC's constraints. PRC's big population = with big demographic curse but also big demographic divident post 2050s. But they don't cancel each other out. Likelt follow JP/SKR trend where TFR collapsed in the 80s/90s but GDP increased 500% because workforce was net gaining skilled/productive people, while losing unskilled. JP (and later SKR) are/will only entering process of real stagnation when TFR cannot replace level of skilled labour at parity. Which for PRC is a post 2050 problem and even then countries will be competing with a PRC roughly 3-5x larger than now.

On the actual demographic curse of aging, the blessings of huge segment of PRC old getting old before they get rich is there simply isn't going to be high expectations for advanced economy levels of welfare and social support. There's a reason PRC has 90% (96% in rural where poor concentrates) home ownership and very high household savings rate. Old expects to weather most of retirement without substantial state support and increasingly family support since they don't want to burden future gens. If you look at JP, old are basically rotting/dying alone, unceremoniously. In JP it's called Kodokushi, in SKR, it's godoksa, it's happening in HK as well. In households that pressure young for support, you know what the east-asian human response to that is? Being miserable whiel working even harder. Half the reason JP/SKR/TW lead in high end industries they currently dominate is because those societies have resigned to working 100% harder for 10% competitve advantage.

Thank you for writing it out, I think people are sort of in denial and have been for a solid decade now.

Arguments about China’s inevitable collapse are more about comfort than about the an reality, because as you have mentioned if you think at all seriously about the demographics argument it just does not make sense.

I think the biggest risk for China demographically is if their aging population translates to an extremely conservative, risk-averse government/society that harms their technological progress, as has happened with Japan (ie. top multinationals stuck in the 80s with fax machines, paper, etc.)