The Meaning of Life, the Universe, and Everything.
I have some random knowledge from patch notes, experiments, and youtube videos. But I have a lot of holes in my knowledge as I'm trying to construct some iron farms, and I'm getting inconsistent results.
Here is a list of what I know, if I have only one source it remains unconfirmed:
1. IG spawns in a 16 block radius from the villager that starts the gossip (from IG wiki page)
2. IG requires 5 votes during gossip for a spawn (from patch notes and confirmed from experiments)
3. IG spawns on a solid block only, within transparent or air blocks.(from IG wiki page)
4. For a villager to gossip they need to complete a work day cycle, sleeping in a bed, access to a owned profession block, and access to village center (Based mostly off experiments)
5. Bell no longer is required to determine location of gossip. (from youtube video, and confirmed from experiments)
6. Village center is determined by center point of all villagers current location at the a specified time in day (guess based on experiments)
7. Number of golems that can exist within a village is at least 1 golem per 5 population. (I had villages that had 3 golems walking around with pop of 12, I've seen more in naturally generated villages like more golems than villagers. bug?)
8. IG seems to spawn either in the morning 0, noon 12000, and night 24000 just before they goto bed (from experiments, but I'm largely unsure about this)
9. IG will not spawn on solid block below y=5. Just fixed one of my farms by raising it up 1 block. Superflat worlds land is y=4. (experiment farm with solid blocks at y=4, sat for 5 minecraft days with no IG)
Let me know if something is not correct or if you can confirm something.