China is massively lying about their population. It is not 1.4 billion people. It may be as low at 600 million.
In 1950 the population of China was estimated at 530 to 540 million, when the CCP took control.
It requires a fertility rate of 3.3 to triple the population in 50 years.
In 1959 the great famine in China resulted in an estimated 30 million deaths.
From 1979 to 2015 China had a one child policy.
Mathematically, there is simply no way for the population to have grown from 540 million to 1.4 billion between 1950 and 2020.
China is rapidly aging due to the one child policy which was too successful.
China has a long history of publishing fake economic data. There is zero reason to assume their official population data is accurate.