China desperately still needs to reduce its population. The future isn't in subsistence farming. If humans survive the threat of wars, natural disasters, climate change, peak oil, pandemics etc, we are on the verge of new technological and industrial revolutions. There's a balance between mouths to feed and labour value, individual productivity... maybe the population decline in China has been a little too dramatic which could potentially cause volatility in less obvious ways but as things stand and as the population ages, the fact still remains that China's population (yes even the young <30 population) is very much still high, possibly even too high for the coming era of unprecedented changes to how societies will function, assuming things go well and proceed normally for Earth.
Anyone saying China's population is too low or rather will be too low, doesn't understand numbers and demographics. The only potential issue is the volatility that a sudden change in demographics may cause but I doubt it'll be that bad. Eventually the birth rates in China are going to reach Japan/South Korea/ Western nations levels but this is actually opportunity and given the high ecological and economic costs for consumption, sooner rather than later, countries with high birth rates will become increasingly poor. Things are getting increasingly expensive and energy/food/water/ COx/ SOx are getting more and more unaffordable. India is in a world of hurt in this respect. India as a nation is going to collapse from one of many things. Possibly a combination of factors within this century. Most intelligent people who are not blinded by liberalism can see this. India's problems require miracles coinciding, China's requires some stimulus packages if it ever even comes to that level of desperation for more people... lol more Chinese people.