Confucian stock refers to the Chinese stock. It is no coincidence that countries with the worst in fertility are homogeneously Chinese or have a overwhelming Chinese population as is the case in Singapore.
Looks like I often have to conduct history lessons for you.
Back in 1970, Lee Kuan Yen looked at the population projections and fertility levels and feared a lemming colony on the horizon. A slew of measures were introduced - from voluntary sterilization to tax and education policies ( e.g: lower priority for 3rd child's). "Stop at Two" was the slogan and there were even stamps to commemorate the campaign.
Fast forward to 1980, just ten years latter and fertility rates have dipped below replacement levels.
The point is fertility levels are significant and massive game changers. You need to look at projections not just how many Chinamen there are now.