There is a limit to how many humans the earth can support...
Take a page of China's book and limit couples to 2 or less. Unless the woman conceives more than 2 sperms during sex. I don't have any kids and don't to have any.
The forced (fines, bad schools, etc) one child thing didn't work too well in China. We shall see how their 2 child works. The main problem with one child was Chinese parents wanting boys if only allowed one kid.
2 billion people on Earth are under the age of 15.