> Social security and pensions, for example, are structured not unlike a pyramid scheme: for every old person we should have more than one working young person.

I'm from a western country and I agree with your statement and have a similar fear. My country is doomed because of the pension system.

BUT this doesn't apply to China. Their system isn't structured this way, therefore this is mostly irrelevant for them.

As long as China have a working population bigger than most countries, as well such amazing universities, they will perform better than all those countries.

Even with the population decline, they'll still have more able workers than all western countries for at least the next 100 years.

Let that sink in.