Decision-making bodies become less effective beyond a small size.
Parkinson put the point of ineffectiveness between 19 and 22 members. Modern group research broadly supports a much lower ceiling, with meeting effectiveness falling sharply above about seven.
In practice
- A board of nineteen discusses the estate strategy for ninety minutes and refers it to a subcommittee of four, which settles it in twenty.
- A project meeting of twelve reaches the decision the same three people would have reached before lunch, and eight of the twelve never speak.