It's only in the well developed western world. Third world countries have the 'capacity' to almost double world population (in case of medium growth scenario,

It's only in the well developed western world. Third world countries have the 'capacity' to almost double world population (in case of medium growth scenario, hopefully population size will plateau at around 13 billion, I do not think that optimistic rapid decline is possible without rational action of global intervention to reduce population growth [0]), which IMHO sounds catastrophic. Because for next 50-100 years global population will be increasing rapidly and hopefully will stabilise after that, without any prospects of reduction for probably double of that time frame. Even if the population will start to decrease I think it may take at least few ages to reduce population size to what is today. [0] https://en.wikipedia.org/wiki/File:World-Population-1800-2100.svg https://en.wikipedia.org/wiki/File:World-Population-1800-210... , https://en.wikipedia.org/wiki/World_population_estimates https://en.wikipedia.org/wiki/World_population_estimates