Meeting duration as a function of the number of participants

My conjecture is that a meeting involving \(N\) participants takes a time \(T\) given by:

\[T(N) \, \text{[in hours]} \, = \exp (N/\; 7) -1\]This only applies to unstructured meetings (with no official hierarchy) and is fairly insensitive to the topic at hand. The time ranges from 20 minutes for \(N=2\) to 4½ hours for \(N=12\).

For any meeting larger than about ten attendees one should either designate a chairman or schedule a lunch break.