Look at a population pyramid.
This site has done nice animated options: https://chartingtheglobe.com/demographics/population-pyramid
If you want to see more regional overviews, then the CIA also has some nice selections here:
https://www.cia.gov/the-world-factbook/references/population-pyramids-by-region/
The main issue is that the population is getting older. Not enough new borns to pay taxes to care for the old people in twenty years. This can only be solved by immigration from countries with higher birthrates.