By Demographics I mean population as seen in a Population Pyramid. Population lets you have soldiers, workers, social nets, etc. Japan was one of the first countries whose demographic bomb began to go off. To mitigate it Japan moved production facilities out of Japan. For example, Toyota vehicles are now made manufactured outside of Japan in places like Mexico and the U.S. This means the lack of workers in Japan is mitigated by the work being done in Mexico, while profits flow back to Japan to keep their retirees alive. Mexico has good demographics.
There's no way around Demographics, it takes 18 years to produce an 18 year old, and even if these countries were to start having kids now, they wouldn't see benefits economically until 18 years from now.
Here's China's Demographics in a population pyramid. The next cohort under the 30-34 bulge has 10 million less people (10 million less workers). The next cohort has 9 million less people (Another 9 million less workers). When the current 30 and 34 year olds retire in China, there won't be enough workers to replace them. Their economy is going to massively contract...hard. Keep in mind that China massively pads their numbers for demographics, so it's even worse than this chart shows.
https://www.populationpyramid.net/china/2019/
Here's Turkey. Notice the base is not shrinking like it is in China:
https://www.populationpyramid.net/turkey/2019/
Here's Mexico. Notice the same thing as Turkey, good demographics:
https://www.populationpyramid.net/mexico/2019
Here's Germany. Look how horrendous that graph is. That's because their births have been far below replacement level (2 per parents) for decades. Germany is in danger of imploding:
https://www.populationpyramid.net/germany/2019/
The United States is shrinking, but vastly slower than all the rest of the West (all us Evangelicals with 5+ kids are doing that). Plus we have immigration for a net gain:
https://www.populationpyramid.net/united-states-of-america/2019/
In other words, all the Western Countries, plus China and Russia are going to be hemorrhaging population except for the U.S. While Mexico, Turkey, Argentina and Africa are growing or stable in population. Putin is making a move on Ukraine because his demographics are so bad that if he waits a decade he won't have an army left, they'll all be old.
And when Turkey needs more farmland to feed their population, a stable Turkish army against hollowed-out European demographics made up of mostly old retirees with very few young people (I.E soldiers) won't go well for Europe. Europe will be very interesting in the next 50 years.