Here are four self-explanatory graphs.
Working age population (15-64 years old) levelled then began falling. I think it will be catching up with fall observed in OECD countries, which began earlier.
Falling in the number of young people (less than 15 years ole).
Falling, followed by a flat fertility rate (child per woman).
Increase in the number of old people (older than 64).
The answer should be clear.