I think I've solved it; the reason for the downward spiral of Village Participation is because the all of the wenches have absconded! Or been absconded! Obvious, when you think about it, eh?
OK, sure, we've had a few nibblings and patterings and munchings by a couple of wenches but this is a very rare event these days.
The mystery is: wha' happened??
Some theories:
1. Night Owl finally perfected his Wench Potion, and they are all now subservient slaves in his mini-castle where they ply him with beer and pretzels.
2. The stench in the Bastard Bar finally overcome their olfactory defenses, and they all went home to find jobs with Google and/or Facebook.
3. The specter of the previous event of the Execution of All Females (hey, I was just trying to right a few minor wrongs!) has returned, and the wenches are hiding in dark tiny corners throughout the land.
4. They were lured away by the Dark Side of Humanity (good looks, charisma, and money, all of which are sadly lacking in Bastard Bar Regulars).
5. The Vestibule imploded, and thus the Gathering Spell was broken, allowing the wenches to flee.
So the solution is simple: we just figure out the cause, and then apply the remedy: voila! Wenches return!