I don’t think it needs to be that high. The average person is not competent on modern technology. Any mass casualties, in my opinion 75% or above, could cause our technology base to drop 100 years. It would also be important if a single area was no affected. Energy production, food production, medical production, most manufacturing is only capable through the efforts of many people understanding a portion of the complex system.
I read how penicillin was first produced. I couldn’t do it on my own or with 10 random people.
Speaking of penicillin:
It has been noted that in North Africa in the 19th c, tribesmen used an ointment derived from the mold on harnesses and saddles. A French doctor by the name of Ernest Duchesne pointed this out but his peers ignored him.
https://en.wikipedia.org/wiki/Ernest_Duchesne
Back in the 1st c BC, Marcus Terentius Varro wrote:
“there are bred certain minute creatures which cannot be seen by the eyes, but which float in the air and enter the body through the mouth and nose and cause serious diseases.”
His peers ignored him too.