How much of the world could die without civilization ending?

[Orsalis]

I think if people just spontaneously died, with no real threat to respond to, say like, a plague or zombies or some shit, I'd say that only about 20-30% of the population would have to remain to keep a complete social structure as it is now. I mean, if you dipped lower, there would still be some ATTEMPT at it, but I doubt we'd have enough manpower or universal skills to be able to run everything.

Might actually be nice if 80% of people just went away >_>