Every country that Westernises in living standards, industrialises, whatever you want to call it gets a sub replacement birth rate. Niggers are having 5 kids per woman right now, but as less need for little farmhands is present, medicine makes sure your kid won't die, people move into cities (large families less practical) and contraceptives become more available even their total fertility rate is decreasing.
Even in semi-based (they still let women into higher education though wtf) countries like Iran, the average woman is having less than 2.1 kids (the replacement rate), so not enough babies are being born to replenish the population.
In many places where this is happening the population is still increasing because old fucks live longer than before and a larger cohort of elderly can add to the total, but in sufficiently late-stage places like Japan (famous example), Germany, Eastern Europe or the USA (the non-hispanic white population, ie the group that was both in the USA and exposed to first world living standards at the same time the longest, is actually shrinking now and the average white American is almost 40 years old and aging so it will inevitably be unable to replenish itself from here on out) the population has begun straight up shrinking because first worlders do not have enough babies to replace the older generations.
Every baby bonus to foids, subsidy for single mothers' bastard kids and handouts for reproducing in general have not halted the long term decline in births and inevitable shrinkage of the population. This is an industrial problem - no pre-modern society has had as low a fertility rate as ours do now, much less recovered from it. Instead of actually trying to fix it, lazy governments just import more people, raise the retirement age so older people have to support themselves or just straight up do nothing.
Imagine how bad this will be when a place like China or India (China has a very low TFR due to the legacy of the one child policy) starts shrinking and have to take care of their old people but are too big to replace the losses with immigrants, or the west has been turned into Brazil (just a multiracial hub for all kinds of wageslave to be exploited) by immigrants and the average native is something ridiculous like 50 years old so they have absolutely no way of managing their elderly without cutting off their pensions and forcing them into concentration camp-like conditions so they cost less to feed while being useless, while the tax burden still grinds young people even further into the ground and depresses fertility even faster. It will be much harder to cope or recieve neetbux when the economy has been nuked by a shrinkage in its size via less people.
Look up the mouse utopia experiment, certain conditions will depress the fertility of social animals and it won't go up even as the society begins to nosedive.