RE: Not having kids causes economic stagnation.
But China has recently changed their policy to allow TWO CHILDREN per family.
Once a society is used to no children, allowing them more than one is not going to convince them to follow through.
Russia hasn’t recovered its love for children and it has been thirty years since the end of communism for them.
And too few are interested—thus incentives.
And all those one-child boys (and a few girls) want all the latest toys and Iphones and cars and etc. They are not willing to wait for this, one of their parents or grandparents will give it to them.
They do not want to work, nor do they want to serve in the military. It is becoming a very acute problem in China, and killing off the 80 year olds does not satisfy the military and factory need.
An average of 2.1 children per woman is considered replacement level in a country with modern medical care.
However, city dwellers may well consider having multiple children to be a financial burden which interferes with their desired lifestyle.