A pictorial description of the relationship between occurrences and more serious incidents and accidents.
In his 1931 book "Industrial Accident Prevention, A Scientific Approach", Herbert W Heinrich put forward the following concept that became known as Heinrich's Law:
in a workplace, for every accident that causes a major injury, there are 29 accidents that cause minor injuries and 300 accidents that cause no injuries.
This is commonly depicted as a pyramid (in this case with the number of minor incidents shown as 30 for simplicity):
Heinrich's law is based on probability and assumes that the number of accidents is inversely proportional to the severity of those accidents. It leads to the conclusion that minimising the number of minor incidents will lead to a reduction in major accidents, which is not necessarily the case.