Could someone clarify what the author means by "Women in developed affluent countries tend to have 2-3 children (or 0-1 children)"? Does he mean that in some c

Could someone clarify what the author means by "Women in developed affluent countries tend to have 2-3 children (or 0-1 children)"? Does he mean that in some countries the range is 2-3 and in others 0-1? Or is it that there are two peaks in the histogram?