I have read the stats that say 80% or so of all accidents are from human error. That is comparatively easy to measure. Why? There's been a reportable incident or accident which is investigated.
What is much harder to measure is the number of situations that humans have sorted out before they have become accidents/incidents. By humans I mean engineers, ATC and pilots. Humans stop many incidents/accidents from happening.
Humans generally want to live to enjoy their day off.