Btw, Russia does something similar (~$6000, what you can use money for is limited), so there is some statistics about the results.
I agree with the spirit of your suggestion -- often "it is known" that something couldn't possibly work, based only on armchair reasoning, or one half-assed attempt made a few decades ago, in a different country, with N=20.
That said, literally cash for babies feels somewhat dysgenic (though, maybe if we actually did the experiment, the results might surprise us). It seems like it would appeal most to people with short-term thinking, the most poor people (which is probably correlated with various dysfunctions), and psychopaths who only want cash and don't care about what happens to the baby afterwards. I don't insist that a good policy needs to appeal to the elites, but it would be nice if it appealed to the average people more than to those at the bottom.
I would prefer financial support in a form of free kindergartens, free school lunches, free health insurance for children (if there are countries that don't already have that), even free babysitting in the afternoons and weekends. Make it a few thousand dollars a year, but with vouchers instead of cash.
I could also imagine various kinds of non-financial support (on top of the financial support, not as an alternative), such as more libraries specialized for children, cheap tutoring, coordinating second-hand selling and buying things for children, etc.
Also, build more playgrounds, and buildings that can only be used for activities for kids (clubs, etc.).
I agree there's better ways to do this, but:
a) the point is even the brute force stupid ways are doable and would likely work. Obviously try to the cleverer ways first.
b) the drop in fertility rate is so bad and so destructive that if we can't get this done the good way, even the dysgenic way is very much worth it.
I thought from the title this was going to be about encouraging us — us, the people reading this — to reproduce. What is the birth rate among LW participants?
Strongly subsidizing the costs of raising children (and not just in financial terms) would likely provide more pro-social results than a large one-time lump payment. However, that won't do much for folks skipping out on children because they think humanity is doomed shortly anyway.
I just saw on twitter someone claiming that we "don't know how to raise the birth rate". No need to link them, it's a fairly common sentiment.
Have you actually tried raising the birth rate? For real, as in actually put in any effort?
Let's run the numbers on the stupidest possible thing that could work. Offer anyone who has a baby 50,000 dollars, tax free, no questions asked.
The median household income in the USA post tax is under 70,000 dollars. 50,000 dollars is a life changing amount for a large percentage of Americans. I would be shocked if a policy like this didn't send birth rates through the roof. Heck, I earn way more than that and I'd probably have more kids with a policy like that!
So how much would it cost?
There's about 3.5 million births a year in the USA. That comes to 175 billion dollars, or 3% of the federal budget. Even if the policy is incredibly successful and doubles birth, that comes to 6% of the federal budget.
That's about half of defense spending. It seems to me that ensuring the country has a future in 30 years is at least as valuable as maintaining the pax Americana. Even more it's a prerequisite to do so, unless we've invented robot soldiers by then.
Not convinced it would work? So test it out! Pick 20 counties randomly by lottery to implement this policy for, for 5 years. If it works well expand to the whole country.
But no, we've got no clue how to raise the birth rate, nothing to be done here, let's all go extinct.