I have been working with small groups of one kind or the other for over 40 years in churches and higher education as a pastor and as a chief administrator responsible for the viability of these groups. As a practitioner I have learned from experimentation with groups about what is called “minimal sustainability”. Minimal sustainability is the minimal number of total members that a small study group needs to sustain itself in light of the normal absenteeism that will randomly occur as people encounter conflicts in their schedules, other obligations, sickness, work schedules, other plans, and so on.
If core members of the group are asked to commit to a weekly study that lasts for only a few weeks in duration, not missing except for unavoidable conflicts in schedule or sickness, and notifying a leader of their impending absence, one can start a group with 10 and expect to have at least 5 or 7 in attendance each week. (If the group meets in a home or there are other dynamics at play the number could be higher.) These members are willing to make a high level of commitment for a study limited to a few weeks.
If you add no expectation other than that the participants will commit to each other to notify a group leader of their impending absence of a session as they occur, minimal sustainability will still require several more core members than in the high commitment group in order to sustain the group. The total number of core members are the people that will end out participating in the group at least once over a 6-week period in an ongoing group without a planned ending date. Most will attend more often than that.
My observation has been that without this one expectation, a small group of around 15 total members (those who will participate at least once in 6 weeks) that meets weekly with no limit on duration of the study can expect to drop to 3 participants a few times a year. Increasing the commitment that the participants make has a direct impact on raising this number. For some reason, people are motivated to commit, especially when a group begins, for reasons that do not continue to motivate them over time unless members make commitments that work to hold them accountable.
To increase the effectiveness of a small church group, ask members to commit to notifying a leader if they decide to or have to miss a session. The minimal sustainability will go up just enough to keep everyone motivated. The group can select a leader to be that contact person and follow up with members who are not attending.
Stephen Williams