The Root Causes of Anything

I'm working on a book about failure. My motto of the moment is: One person's failure is another person's revenue stream.

I found this chart in a presentation "Human Factors in Aviation" which is a summary of 86 aircraft disasters in North America by David J. Taylor

Complete Article

Causes/ major contributory factor	% of accidents in which this was a factor
Pilot deviated from basic operational procedures	33
Inadequate cross-check by second crew member	26
Design faults	13
Maintenance and inspection deficiencies	12
Absence of approach guidance	10
Captain ignored crew inputs	10
Air traffic control failures or errors	9
Improper crew response during abnormal conditions	9
Insufficient or incorrect weather information	8
Runway hazards	7
Air traffic control/crew communication deficiencies	6
Improper decision to land	6

So is it not clear that these can be grouped into five groups? Human, Procedural, Mechanical, and Environmental, with a side order of Detection Issues?

And of all of these do they not boil down to human, at some point?