@WellAgedYeah, we have articles like this in local papers like once monthly for the past two decades with headlines screaming "we're dying out" or other words to that effect. And popular opinion, is, basically, "Meh. So what?"
You can't scare people into having babies. The more you're scaremongering the less children you get. I also think the "economy" is kind of red herring there. I haven't seen data breakdowns by income groups, but won't be surprised by trends being flat for all. Traditionally it's been poor and very poor who had the many children offsetting the planned smaller families of the rich. Now the first world poor are actually rich in practice, and others are catching up. The upper rich actually may already have more children by now, or that's a trend to watch after. The rich should advertise having big families, no matter how disordered.
The big elephant is the "I won't have a baby that turns my life upside down," and ever increasing age of a first child. That trend is even worse news on top of the childbirth rate as such.
The fertility window being roughly 15 to 45, it conveniently divides into 20 childbearing slots of 18 months each. Boys are nearly irrelevant as long we have a few around; to understand population dynamics all we need to know about are daughters.
Compare: a girl having a daughter at fifteen who has a daughter at fifteen who has a daughter at fifteen; in thirty years we have population (46, 31, 16, 1). If each had another child at thirty, the population is (46, 31, 16, 16, 1, 1, 1). Lets add a third child at 45 for a (46, 31, 16, 16, 1, 1, 1, 1) to see how dramatic this can become, as now we have four same age newborns descending from our original woman who had only three children total: a child, a grandchild, two greatgrandchildren, and one great-great-grandchild, all the same age.
(That's about how I have second cousin twice removed who's my age.)
Even having the same three daughters late in life, let's say at 36, 39 and 42 in the same thirty years we have a population (46, 10, 7, 4) and at the same trend will have to wait another 26 years for the next child.
The outcomes in 75 years are now:
(91, 55, 52, 49, 19, 16, 16, 13, 13, 13, 10, 10, 7)
vs
(91, 76, 51, 51, 36, 36, 36, 36, 21, 21, 21, 21, 21, 21, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6)
In the above teen pregnancy case. Yes, that's 12 six year old by each woman having only the same three children (assumed daughters or having available female partner of the same age) at 15, 30, and 45 respectively for a showcase algorithmic case as opposed to having the same three children at 35+. Extending this further it will become more and more dramatic. Having the early child case less spaced out will too, but I wanted to point out how generations overlap. Having three children at 15,17,19 and so on for each of descendants in 75 years will produce a population of
(91, 76,74,72, 61, 59,59, 57,57,57, 55,55,53, 46, 44,44,44, 42, 42,42, 42,42,42, 40,40, 40,40,40, 40,40, 38,38,38,38,38, 36,36,36, 34, 31, 29,29,29,29, 27,27,27,27, 27,27,27,27,27,27, 25,25,25, 25,25,25,25,25,25, 25,25,25,25,25,25, 23,23,23,23,23,23, 23,23,23,23,23,23, 23,23,23,23,23,23, 21,21,21,21,21,21,
21,21,21,21,21,21, 21,21,21,21,21,21, 19,19,19,19,19,19, 19,19,19,19, 17,17,17,17, 16, 15, 14,14,14,14, 12, 12,12,12, 12,12,12, 12,12,12, 12,12,12,12,12,12, 10,10,10, 10,10,10, 10,10,10, 10,10,10,10,10,10,
10,10,10,10,10,10, 10,10,10,10,10,10,
8,8,8, 8,8,8, 8,8,8,8,8,8, 8,8,8,8,8,8, 8,8,8,8,8,8, 8,8,8,8,8,8, 8,8,8,8,8,8, 8,8,8,8,8,8, 6,6,6, 6,6,6,6,6,6, 6,6,6,6,6,6, 6,6,6,6,6,6, 6,6,6,6,6,6, 6,6,6,6,6,6, 6,6,6,6,6,6, 6,6,6,6,6,6, 6,6,6, 4,4,4,4,4,4, 4,4,4,4,4,4, 4,4,4,4,4,4, 4,4,4,4,4,4, 4,4,4,4,4,4, 4,4,4, 4,4,4,4,4,4, 4,4,4,4, 2,2,2,2,2,2, 2,2,2,2,2,2, 2,2,2, 2,2,2,2,2,2, 2,2,2,2, 2,2,2,2, 1, 0,0,0,0,0, 0,0,0,0,0, 0,0,0,0,0)
Yes, to reiterate, those all are descendants of a single 15 years old girl if everyone have just the same three children as fast as they possibly can. There's 12, 25, 343 descendants after 75 years all at the same R=3 but different childbirth age. Human population can rebound very quickly if they're going at it. Consider, in this last scenario nobody had any more children after turning twenty, while there's 25 more fertile years, an unused potential for up to 18 additional children for each excluding twin chances. With R=20 arbitrary small initial population can repopulate the world to 10B in a couple centuries only restricted by resource management.
If an ambitious and unrestricted ruler seriously wants to rejuvenate the society, they want to see a high school class full of baby bumps.
The original nazi tried to do just that. They coopted FKK (Free Body Culture = philosophical nudist movement) to send school kids to two month summer camps with no clothes allowed, ostensibly to rudge them up, living in tents with minimal oversight. Yes, many girls ended up knocked up, and got called Hitler's Brides.
What a country with repopulating directive should look after is consequences free teenage pregnancy. I mean, the girl gets pregnant in a more or less pre-planned directly or tacitly state supported event, keep going to school with a belly showing with no harassment for that, pushes the baby out and keeps going to school and parties a week or two later care free, proceeding to college as if nothing happened. And yes, they will hate it. The country will have to seek to place the baby with her older relatives or otherwise, or better yet pick it up 100% covered.
So we will have a mandatory childbirth on public high school curriculum for every able female student. So why not learn childcare right there? Roll it all in one, school, daycare and orphanage for the state owned schoolborn shared parentless children who in under twenty years will be independent population reproducing itself effectively. Only really need to mandate one schoolborn baby. Not at all that disruptive, me thinks. After graduation she goes to college or whatever, get married if she prefers, have private babies if so inclined. Only need another R=1 on average there. Can tolerate even less if some of schoolborn girls are rolled into full time human farms with local R=20 producing adoptees or holiday children for rent.
Well... yes, that's like only what crazy commies could possibly attempt.
But consider that many a nazi in Europe are in fact socialist at heart. In very name: national socialist. Yes, the implementation usually soon flip into a kleptocracy oligarchy, in effect even USSR did to some extent only wasn't as obvious about it. But the theory is there, they are for the people, only for people of an in-tribe of some sort. So, the unpacked ideal is a caste system, actually. That offers other interesting possibilities, obviously. All the while formally upholding most of the freedoms (mandatory baby at school asside) for that core desired population, at least nominally.
Or alternatively, consider ultra-liberal backlashes after nazi failure. For the same effect.