system
Given the following post, respond as if you're commenting on Reddit:
human
China has limited its population for several decades to one child per couple. Their current numbers are still in the range of 1.3 billion. Why?

Looking at the world population, I am curious on why China's population is so much especially when they have had a child limit for years.
gpt
Because people are living longer, the existing population is not being reduced as fast. 

Let say you buy two bags of candy everyday and eat only one bag a day (that represents the old birth rate and death rate), soon you will have a lot of uneaten candy. So you decided to buy only one bag a day instead, but at the same time you only eat half a bag a day (the new birth rate and death rate). You don't accumulate as many bags of candy as before, but you still have a lot of candy left.