IMHO Low birth rates are a symptom of growing systemic problems that often plague complex systems. A Global world is actually the mother of all complex systems, and indeed we often pay for that complexity by overworking our citizens and with oil, both are things in sharp decline.
The birth rate thing is a curious phenomena with only one real common factor, once even partially integrated into this big thing we call Globalization, the effects of modernity appear to be sterility. However those countries still need young people (Thus the elite fixation with migration and multiculturalism) with the hope of bringing in young fresh laborers and people to keep rents and property values higher. This is the Labour Arbitrage that @
Nadiru mentions. So our territories actually are engaged in a contradiction, WE NEED those parts of the world that aren't integrated into global civilization yet, but the logics of globalization and Neo-Liberal capitalism necessitate integration, expansion and new markets. Soon the only places left without a McDonalds will be North Sentinel Island. Nadiru points out that often the Western States have massive obligations in taxes, in the EU its often a generous welfare state, in the US its the sum total cost of being the worlds biggest bully to engage in a kind of Hegemonic Stability Empire. Either way the countries both have declining births and thus needed people, but they also need to expand and keep cash flowing.
What happens when at last even North Sentinel Island has a McDonalds and the new iPhone? Well, likely by then death for the Global world order, because as @
kail points out, globalism isn't new and even globalization goes back to the Bronze Age. Of course what he fails to mention is the cost of these systems and how all of the past instances of it have collapsed, often proportionally to how big they are.
As Dr. Tainter notes, we fuel our complexity with oil, I would add we also fuel it with people. But as the Earth greys (97% of the earths people live in countries with Demographic instability/decline) and the black blood that flows through its veins becomes more expensive and more precious, this system will face the great problem, that being the issues caused by past Solutions to other problems. Be it the issues of Climate Change, mass migrations of people caused by climate change and war, domestic instability as Nationalists and Internationalists clash for their countries future, ecological degradation, the class struggle as the owners of those robots don't want to do anything for displaced workers and workers being pissed, likelihood of future pandemic diseases, economic instability caused by demand issues due to demographic decline and the problems of Demographic Decline in general. All will be faced at once and all will end the Globalist world.
Me and @
Connal and @
Yvaelle frequently go at odds over this, with the two of them having a greater faith in the future than I, Connal especially bets that Humanities technical brilliance will outrun death, I placed most of my chips on black (Death) though a part of me is cautiously hopeful that my bet was wrong and Connal and Yvaelle are right.