Education, more specifically of women. Colleges today are majority female. They don't invest that time to graduate and raise large families. Birth rates in the world. Education still coincides today. Look at the skew in France, those are not native French being born..
education for city folk and liberals, men and women, is the cause for them to have fewer children to love and take care of, I have little doubt.
country folk just cant afford them. I would have loved to have had 4 or 5 more kids but as I said my wife couldn't have them, I wasn't getting rid of her for that BUT I surely don't know how I would have been able to feed and clothe them. I would have figured something out though.
city folks think very differently than we do down in the woods. they think about themselves first and foremost. maybe it is the education they are getting. I do not know.
it may well have to do with years ago the state asking small communities to add diversity to our families and making meeting woman from other places more available to those same small communities. that way we didn't have to marry our first cousins and all dontcha know.