In the last two years, the popularity of foxi (buddha-like apathy) and more recently, tangping (lying flat and abandoning the rat race), show the degree of stress young people are under. Stressed out people are less likely to form families and have children. China needs more children.
Here's a video that discusses the rat race and potential effects: https://www.youtube.com/watch?v=WDc8-lNSFR0