Interview with Michael Mankins, Head of Bain & Company's North America Organization Practice and one of the most influential consultants in the world "Effective meetings need to have a clear agenda and limit on number of participants", commented Michael Mankins, Head of Bain & Company's North America Organization Practice. "For example, working-level meetings should not exceed seven participants. This is because of 'Rule of Seven', where every person added to a group over seven reduces effectiveness by 10 percent", he added.