Yet only 10% can be attributed solely to actual individuals performing badly. Performing badly means deliberate or negligent acts: working under the influence of performance-impairing chemicals (legal or not), working when overtired, working when significantly bothered by personal concerns,
working without paying reasonable attention (e.g., daydreaming, etc.), working when too ill (physically or psychologically), working without disclosing important physical limitations that would otherwise disqualify from work, and other similar situations.