[nostrademons]

Right. Other examples of a population bottleneck include Communist China's Great Famine + Cultural Revolution (killed ~5% overall, up to 18% in some provinces), and WW2 (~3.5% overall, 15-18% in some regions like Poland, Lithuania, and the Soviet Union). In WW2 the infrastructure was destroyed, and that led to the post-WW2 boom (even in losing countries!) as it was rebuilt with modern technology.

WW3 will result in the collapse of globalization, but it's very unlikely that it'll affect all regions equally, just like how the U.S. ended up as the big winner because it was all fought on foreign soil. Whichever regions manage to stay out of WW3 will likely enjoy the economic fruits of increased technology + being the engine of rebuilding for the remnants of the rest of the world.

[KineticLensman]

> In WW2 the infrastructure was destroyed

But it was rebuilt partly using massive Marshall plan investment which wouldn't exist in a world where several billion people have just died.

[nostrademons]

Why wouldn't a similar Marshall plan exist in a post-WW3 world? Wars don't affect all areas equally, and don't kill everybody. Even if you assume that 50% of humanity dies (way worse than WW2, and worse than every known war in history), that still leaves a population of 4 billion, which is what it was in 1975, 30 years after the Marshall plan.

[KineticLensman]

> Why wouldn't a similar Marshall plan exist in a post-WW3 world? Wars don't affect all areas equally, and don't kill everybody.

Agree, but the Marshall plan only worked because it's provider (the US) was essentially unaffected by the war and had money to burn. I can't see that a war that killed billions wouldn't damage the superpowers, who would be the primary providers of post-war aid.

[nostrademons]

The U.S. wasn't a (geopolitical) superpower before WW2, although it was definitely a strong rising economic power. Britain was considered the world's superpower, with other major Great Powers being the U.S, France, Germany, Italy, Russia, and Japan. The U.S. became a geopolitical superpower by virtue of being the most undamaged of the Great Powers after the war.

Similarly, it's likely that whichever industrialized high-tech region that's unaffected by WW3 would take on the role of the post-war superpower. I can't tell what that be - it could be a country like Brazil, Australia, New Zealand, Scandinavia, Kenya, or a region of an existing superpower like California, Ireland, or the Pearl River Delta - but it's likely that there will be some portion of the globe that is not destroyed and yet still retains enough technical knowledge and capital base to rebuild the rest of the world.