1.2 billion _old_ people. While quantity has a quality all its own, in this case the demographics are not what you want to see if you are predicting long-term Chinese growth just based on population.
Depend on them for what, the cost of a bowl of rice? What is it exactly about 80 year olds that will collapse a country with a brutal government like China has?
You think that a country that has a strong cultural history of venerating their elders is just going to pivot on a dime and decide to put grandma and grandpa onto an iceflow and cut them loose? Those elderly out in the hinterlands are also the people who raised a large fraction of the youth population while their parents were off in Shenzhen pulling shifts at Foxconn.
The other thing to look at in those population distributions, besides the upside-down age distribution, is the absolutely pathological gender imbalance. The number of surplus males under 30 should be keeping Xi Jinping up at night because if there is anything that is going to trigger another revolution it is tens of millions of disaffected young males migrating across the country who eventually get fed up with what they perceive as a dead-end future.
It's a mistake to think in terms of the US only. Because unlike China the US doesn't think that way. And if you include the core part of Team America, it's even steven.
Who is the core part of team America? Because the anglosphere doesn’t even it out I don’t think and Western Europe is not unequivocally on our side in US-China industry competition.
The whole edifice the US, Britain, Japan and Germany created during the cold war to protect societies from the Soviet Union and the Chinese Communists.
The core part defined by long standing military and economic ties is about 1.5 billion people.
Japan is a technical powerhouse but that doesn't inevitably lead to ending hegemony. It requires a lot of other work too.