For many years China had the one child program. They could only have one baby and it was in force so most people did not have enough children to replace the population and now they're paying the price for it.
Of course as any population ages, some people die if you're not not having new people, your population is going to decline.
It's not been a very prosperous year for the world so it's normal that people don't have many babies when things are having economic problems.
