Like I already said it's anime we either got stick figure or Jojo part 1 and honestly I don't undertsand the math.
in my experience most manga do pretty well in making their stories consistent, regardless looking over the math its pretty straightforward
men are monopolized by singular women.
men are born 1 for every 10 women.
1 monogamous marriage irl needs 2 children to match replacement rates because humans are 1:1 irl.
1 monogamous marriage in this manga needs 11 children to match replacement rates since humans are 1:10 in this manga
since women dont share men, 9 women go without children so to replace the married couple 2 children are needed and to replace the childless women 9 more are added
that number balloons when you factor in male harems, 1 woman with 3 men means the other 29 in the 3:30 equation are now childless
replacement rate then becomes 1 women + 3 harem members + 29 childless women = 33 children required
in this world women angry that they have no men would cause a revolt almost immediately upon a male harem policy being legalized