I'm not sure I really understand the argument about declining birth rates, since richer countries will also have the same problem. Article does mention rich countries partially workaround low birth rates by immigration. And poorer countries will struggle to catch up with existing levels of infrastructure in richer countries.
We have surplus billionaires and millionaires in rich countries, and they need be picked through a lottery system and shipped to poorer areas of the world. This is what Chat GPT 4.0 is recommending currently.
https://archive.ph/KNwbz
I'm not sure I really understand the argument about declining birth rates, since richer countries will also have the same problem. Article does mention rich countries partially workaround low birth rates by immigration. And poorer countries will struggle to catch up with existing levels of infrastructure in richer countries.