The MECE principle, pronounced 'me see', is a grouping principle for separating a set of items into subsets that are mutually exclusive and collectively exhaustive.
The MECE principle is useful in the business mapping process where the optimum arrangement of information is exhaustive and does not double count at any level of the hierarchy.
Examples of MECE arrangements include categorizing people by year of birth (assuming all years are known). A non-MECE example would be categorization by nationality, because nationalities are neither mutually exclusive (some people have dual nationality) nor collectively exhaustive (some people have none).
Criticisms
MECE has been criticized for failing to satisfy itself.
Also, MECE thinking can be too limiting as mutual exclusiveness is not necessarily desirable. For instance, while it may be desirable to classify the answers to a question in a MECE framework so as to consider all of them exactly once, forcing the answers themselves to be MECE can be unnecessarily limiting.
Another attribute of MECE thinking is that, by definition, it precludes redundancies. However, there are cases where redundancies are desirable or even necessary.