As defined in IEEE 100, The IEEE Standard Dictionary of Electrical and Electronics Terms, Sixth Edition (as close to "official" as you will likely get):wink: :
diversity factor (1) The ratio of the sum of the individual maximum demands of the subdivisions of the system to the maximum demand of the complete system. Note: Since maximum demand of a system cannot be greater than the sum of the individual demands, the diversity factor will always be equal to or greater than unity.
Robert B. Alexander, P.E.
"I know that you believe you understand what you think the NEC says, but I am not sure you realize that what you read is not what it means." (Corollary to Charlie's Rule)