Still on my Greeley kick, here from A Christmas Wedding, p. 258, viewpoint character speaking, beginning mid-paragraph:
I read somewhere that until the early part of the last century in Western Europe (and much more recently elsewhere) 6.38 pregnancies were required on the average to produce two adults, in other words, for the married couple to reproduce themselves. When we were having children, 6.38 pregnancies would produce seven children (since one must round to the nearest whole child.)
How do we fare? Mom had four children who reached adult, two of whom duely went about reproducing themselves, both achieving that goal (producing two adult children). She went out with a twin tubular pregnancy, giving her a 4/6 ratio of conceptions/live births, or 2/3. (Or do you count attempts, ignoring twin results? That would leave 4/5, AND support the "fertile as a rabbit" theory for women on birth control... Since when she was using it, the whole idea was experimental, I'm sure she contributed to that idea. Still, I think unrelenting pregnancies only lost their place as the number one killer of women of child-baring age when their use became widespread. I'd rather have had a live mother, than be a family of three daughters and a father trying to make it alone. Mom was the glue that held an awfully lot of things together, and still is.)
The sister I "donated" my two children production to (in seventh grade, no less, when her goal was to have 6...) also conceived four, producing three, all of whom made it safely to adulthood, two going into production, and both making that goal (with some excess... nearly enough to cover ALL the unproductive ones among their generation.)
The other sister produced two, who quite accidentally produced only one between them.
I note that Father Greeley has heard, and is discussing the "each one only replace yourselves" idea. I'm not sure when he really wrote it, but one of the on-line book sellers lists it as a 2000 volume. I realize that he can have had the ideas jotted down in a journal, etc. for a LONG time prior to that, but I was glad to see it again surfacing. It needs to gain a lot more airplay, the way the world is going now.