Explore global and national data on population growth, demography, and how they are changing.
ourworldindata.org
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Notice something?
Ya, despite whatever silly notions that your source in the OP opines about, world population is not dropping one single iota at all. It is still growing.
Of course, if you want to focus on growth:
Growth rate may be dropping but even projected out 80 years it still remains positive. Even if the most recent downturn in growth RATE, not actual growth, continues to fall at about the same rate we will still be growing as a population over the next century.
Again, calling this 'extinction' is like thinking a raindrop is actually an asteroid.
This chart sums it up pretty damn well though:
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Humanity progressed quite well for a very long time before reaching the population rates we see today and will do fine if there is a population drop even if it damages much of our current social structure. Perhaps such a decline will teach us, finally, to cease borrowing from an ever growing future to pay for our current messes.
However, such a lesson is more than a 100 years out so I am not putting any stock in such a prediction.