I've recently seen some threads on highly scientific websites about humanity consisting of around 80% NPC's (non-player character) with the other 20% being actual humans.
After reading more into this i was viewing the world differently when going out, just try to look at people when you go out and you'll see it aswell.
How to spot them: NPC's are most likely your average "normies", who autonomously follow group thinking and social trends in order to appear convincingly human. They only talk about mainstream stuff and only have a set number of responses.
It's like they aren't human they are just there to fill space and make it seem like we aren't in a simulation. I'm also 90% sure that mostly NPC's die to terrorist attacks and stuff like that.