Coefficient of Inefficiency is a semi-humorous attempt of C. Northcote Parkinson to define the size of a committee or other decision making body at which it becomes completely inefficient.
Parkinson's Law states that "work expands so as to fill the time available for its completion." A more succinct phrasing also commonly used is "work expands to fill the time available."
S. Bryant, A. Forte, and A. Bruckman. GROUP '05: Proceedings of the 2005 international ACM SIGGROUP conference on Supporting group work, page 1--10. New York, NY, USA, ACM Press, (2005)