Quote Originally Posted by Simon Appleton
Interesting, but it would be useful to indicate the source/status of these statements.
Personal research....

1) Loyalty has no effect.
I've repeatedly seen rebels pop up in provinces with loyalty above 150%.

2) Fog of war has no effect.
I spent two very long campaigns researching this premise. I rigorously built watchtowers everywhere. Not one scrap of my land was invisible. Yet rebels would pop up, even on top of watchtowers.

3) Unrest appears to have no effect.
I've seen rebels appear in provinces with no unrest - provinces which were stable and happy for years. I specifically checked for unrest/devastation. It just doesn't seem related in the long run.

4) The "chance" parameter in descr_rebels.txt seems to have no effect.
I've personally experimented extensively with this field, it doesn't work the way one would expect.

Rebel popups are highly variable. After a few lucky years it's tempting to conclude that a particular solution is working. You might have to play another 50-100 years to see if the theory holds. On various occasions I myself subscribed to Fog-of-War theory, the Unrest theory, the Loyalty theory, etc. Yet each theory was blown away in turn, as additional gameplay disproved it.

Some more ideas I've tested:

5) family members prevent rebels?
No. I once had a rebel pop up 2 times in 4 turns right beside a city containing a family member. In both cases the rebels immediately lay seige to the city!

6) Troops in the countryside prevent rebels?
Not necessarily. I've repeatedly seen rebels pop up rather close to my big intimidating armies. I speculate that a grid of troops could surpress rebels by simply denying them places to pop up. This may work similar to planting forts, but cheaper.

Really, the only luck I've ever had was with extensive fortification of the "countryside". But it was time consuming and I couldn't figure out how to plug all the gaps in the dike.