[1] https://population.un.org/wpp/Graphs/Probabilistic/POP/TOT/9...
[2] https://population.un.org/wpp/Graphs/Probabilistic/POP/TOT/1...
[1] https://population.un.org/wpp/Graphs/Probabilistic/POP/TOT/9...
https://www.nature.com/articles/d41586-021-02522-6
Population growth fell much faster than expected in many places such as Singapore and Iran. Today in Africa people have mobile phones and hence much better access to information on things like birth control.
That Nature article shows that the population expected at 2100 has a realistic range from about 9 Bn to 11 Bn. That difference comes from slightly different assumptions about the change in birth rates in Africa and other places.
From the article :
"In 2014, a group at the International Institute for Applied Systems Analysis (IIASA) in Vienna produced its own forecast. It said that world population is most likely to peak at 9.4 billion around 2070 and will fall to 9 billion by the end of the century. The group’s numbers rose slightly in a 2018 report3 that projected a peak of about 9.8 billion around 2080; a subsequent update has population cresting at a little under 9.7 billion around 2070."
Subsaharan Africa was completely bypassed by the Green Revolution and largely lacks access to basic infrastructure like eg consistent electricity (outside portable fuel powered generators) on the typical small, family, partly subsistence based farm.
It’s not a solved problem with all the geographical and political issues, but it’s quite literally the world’s last frontier for trade.