You will find confident claims all over the governance literature that eight is the ideal board size, or seven, or somewhere between nine and seventeen. Before this series repeats any of them, it is worth actually testing what the evidence says, because the honest answer is more useful than the confident one, and considerably more contested than most governance advice admits.
The origin of the most quoted number
The figure most commonly cited for smaller boards traces back to research from Bain & Company, widely reported as finding that decision-making effectiveness in a group declines by roughly 10 per cent for every member beyond seven. This statistic appears constantly across governance advice, often presented as settled fact. It deserves more scrutiny than it usually receives. The finding is now well over a decade old, is difficult to trace to a single accessible peer-reviewed source, and describes general group decision-making dynamics rather than nonprofit board governance specifically. It is a genuine data point worth knowing, not a law of governance.
What the competing evidence actually shows
Set against the case for smaller boards is a body of evidence pointing the other way. BoardSource's Nonprofit Governance Index, a large-scale survey of nonprofit chief executives and board members, has found that boards in the 15 to 22 member range were rated more effective by their own chief executives and reported stronger governance practices than smaller boards. Separately, surveys by the National Association of Corporate Directors have found that a majority of nonprofit directors consider boards in the 11 to 17 member range to be about right, even as the average nonprofit board surveyed sat closer to 19 or 20 members.
A large-scale academic meta-analysis published in 2026, pooling 346 separate studies across 110 countries, reached a genuinely more nuanced conclusion than either camp: the relationship between board size and organisational performance depends heavily on context. Larger boards bring more resources and expertise but carry higher coordination costs, and which effect dominates varies by sector, regulatory environment, and organisational scale, not by a single universal number.
The honest reading of the evidence is not that eight is right and everyone else is wrong. It is that board size research points in genuinely different directions depending on what you measure and which organisations you study, and any advisor who states a single number as settled science is simplifying past the point the evidence actually supports.
What this means for your board, practically
None of this means board size is an unanswerable question for your specific organisation. It means the right approach is not importing a number from a study of different organisations in a different context, but reasoning from your organisation's actual governance demands.
- What committee structure does your governance actually require? A finance, audit and risk committee, a nominations committee, and possibly others each need enough board members to resource them without the same few people serving on every one.
- What is your actual decision-making pattern? A smaller board genuinely does move faster on operational matters, and if your board spends significant time on operational rather than strategic decisions, that speed advantage is real.
- What does your membership base genuinely need represented? Associations with meaningful geographic, sectoral or modality diversity, a theme relevant to many professional bodies, may need enough seats to represent that diversity without artificially inflating size for its own sake.
- What is your actual capacity to support directors well? A larger board that the organisation cannot properly induct, brief and engage will underperform a smaller board that is genuinely well resourced, regardless of what the raw number suggests.
Most working guidance across the literature, from both the smaller-board and larger-board camps, converges on a workable range for a typical association board somewhere between seven and fifteen members, wide enough to reflect the genuinely mixed evidence, narrow enough to be useful. Where your organisation sits within that range should be a deliberate answer to the committee, decision-making and representation questions above, not a number borrowed from a consultant's slide because it sounded authoritative.
Explore the Board Director course
Want the fully branded, board-ready PDF of this article? Download the whole 52-part series — free.
Until next week,
Annie