[ralfd]

Slatestarcodex has a good roundup of different arguments and metrics (world lead production):

https://slatestarcodex.com/2017/10/15/were-there-dark-ages/

> Although I sympathize with the feelings behind both positions, I say the Dark Ages happened. I think the best evidence we have suggests the fall of Rome (and the period just before) was associated with several centuries of economic and demographic decline, only reaching back to their classical level around 1000 AD. I think it was also associated with a broader intellectual and infrastructure decline, which in some specific ways and some specific fields didn’t reach back up to its Roman level until the Renaissance. I think that common sense – the sense you get when you treat the question of the Dark Age the same as any other question, and try to avoid isolated demands for rigor – says that qualifies for the phrase “Dark Age”.