We do exit surveys of people who leave our (much smaller) society, and we found that maybe two people were causing most of the membership churn. People would join in good faith, go to a meeting, and be shouted at because they're jews. Fine, out they go. We don't notice these individuals very much because they're only at one or two meetings, but over time, keeping them would make our membership about twenty times larger. Comments like: "Guy with white hair and hearing aids said that I was worse than a child molester because I'm a Christian - I don't need to be insulted like this."
This is the same guy that is the reason my wife resigned (she's Southern Baptist).
Our new strategy is to put a stake in the ground regarding this type of behavior, and we've signed up about eighty new members in the past six months with only two departures (no explanation, unfortunately). This compares to an 80% annual turnover.
However, this is off topic, but I always feel it's worth visiting. I have found, though, that this topic degenerates on the JREF forum, so I don't bring it up anymore unless provoked.