Heinrich in 1931 presented a theory on the causes of industrial accidents.  Heinrich found that 88% of accidents had been caused by unsafe acts of people, 10% by mechanical or physical hazards and 2% by Acts of God.  Various safety scholars have disassembles theses studies, but as yet no one has disproven their validity.

When working with companies in various fields, what is often clear is the unreadiness of safety assessors to look at human unsafe acts as causation.  Given the above statistics most businesses should have statistically similar ratios.