My enthusiasm for groups of five women comes from Chris Brookfield sharing his experiences in India working with groups of five women in villages. He spend about seven years extending microfinance into a significant portion of India. His pictures and narratives of these meetings in homes impressed upon me the intimacy and determination that can quickly coalesce among five women who want to act together.

From my experience I do not imagine many such groups made up of men working collaboratively for local action. Men can be enlisted but the cohesion will more often be from a small group of women.

My own experience leads me toward the magic number five--when I want to figure out how to do something and also to get started doing it.

Why five? Significant diversity. Plenty of time for each person to be heard and to hear. Self selection for fit (understanding). Sufficient time for understanding. Significant diversity for action--skills and time and social networks.

Groups size five is not prone to splintering, whereas four easily becomes 2 + 2 or worse 3 + 1. Groups size 3 too easily becomes 4 + 2, 3 + 3, 2 + 2 + 2.

Group size seven does not split easily so it would be my second choice if more diversity is needed and enough passion and time is available.

Groups size eight has same problems as size six.

If this does not match your experience, ignore it.