Yes there are exceptions, but I was talking about the average. The number 2 comes from the current world wide trend. In developed countries the fertility rate

Yes there are exceptions, but I was talking about the average. The number 2 comes from the current world wide trend. In developed countries the fertility rate tumbles down but stops at around 2. So it is believed this is the average bottom. Maybe you like this talk from Hans Rosling: https://www.ted.com/talks/hans_rosling_religions_and_babies https://www.ted.com/talks/hans_rosling_religions_and_babies