Zichen Wang just recently left China state media, he was working for Xinhua if I remember correctly.
The problem with 400 million China is, until you get stable population of 400m with TFR at about 2, firstly you will need to get there from 1.4B, and current level of 1.08 TFR, what it means? It means that every year the level of old population will grow, I am shooting now, but if TFR stays at that level I guess the China's of 400m population will be like 70% grandpas and grandmas and the rest 30% youth and middle age.
Anyway that far projection are not realistic, the 400m China if TFR stays the same is first decades of next century.
What I would focus is to try to get China to increase the TFR to 1.6 or 1.7. I think this is realistic goal and even when population will be still decreasing with that level of TFR the balance of population won't look that tragic, and China won't become the nation of grandpas.
If China can't arrest the TFR collapse before it reaches 400 million, there's no reason to believe it will do so after it reaches 400 million.
I don't understand certain posts above saying "oh, it's fine; everything is fine" to a scenario like that. No, it is not fine. If China's population falls to 400 million by 2100, it'll mean that China has
failed in its attempt to slow demographic decline. In that case, 400 million will become 200 million in another generation, and then 100 million, and so on until the nation is either extinct or irrelevant.
As for mass immigration as a solution, that doesn't work with a population the size of China's. Although, it has happened before in Chinese history. The Eastern Jin Dynasty mass imported "barbarians" to make up for catastrophic population loss as a result of the civil wars near the end of the Han Dynasty. The eventual result was that the "five barbarians" revolted against Eastern Jin rule and established their own dynasties, taking over all of northern China, thus starting centuries of "barbarian" rule in the north. The subsequent Age of Fragmentation was one of the most violent and chaotic periods of Chinese history.
Lesson? You can't replace a large fraction of the population with immigrants in a generation and expect it'll all work out the same. Those immigrants will come with their own cultures and identities. They won't "feel" Chinese and they won't be loyal to the Chinese nation.
The only reason the US was able to avoid this is because it never had an identity to begin with. Everybody was an immigrant, so there was no common culture; consequently, loyalties grouped around "race" and racial conflict was constant. However, the US kept the "white" race the majority for most of its history and played divide and conquer with blacks, Latinos, Asians, etc., so it avoided a successful racial revolt. But we see how American conservatives today are fearful of such a event now that the white population is on the decline; that story has yet to end.
