Nice thread but I've noticed that most of the discussion was focussed on Culture penalties and not so much on Unrest. Jerome was kind enough to provide the rough guidelines on it but it makes me wonder what are the specific factors involved (if any).

Being a player, I would like to know if there's any way we can speed up the decline of Unrest over time. Generally it appears that most towns start with 30% Unrest once you take over them and this gradually declines by a constant 5% over each turn. Adjusting tax rate doesn't seem to make much difference and neither does adjusting garrison size. Governors with traits that increase Unrest have the expected effect when they conquer a new city (making the initial Unrest 35%) but that effect immediately goes away once the governor leaves the city.
I have also noticed a couple of towns which start with 45% and 60% Unrest. It rarely happens though. The town which started with 60% Unrest appeared to have a rebellion recently (was previously under Seleucid rule and occupied by a Seleucid governor). Not sure what happened after my diplomat moved away from the place but the next turn when my troops arrived they found an empty town instead, a higher Unrest than normal and the Seleucid governor was nowhere to be seen.

Some players have complained of a permanent 15% Unrest. Is this true and if it is, why is it so and can it be avoided.