The revolt % you see on any given province in EU or EU2 is a chance per month for that province to revolt in that month. Here are the chances that a given province will revolt at least once in a year, at a certain monthly revolt %:
Code:
:--------------------------------------------------------------------------------
%/year
%/month %/year multi revolts
1 11.4 0.6
2 21.5 2.3
3 31.6 4.9
4 38.7 8.1
5 46.0 11.8
6 52.4 16.0
7 58.1 20.3
8 63.2 24.9
9 67.8 29.5
10 71.8 34.1
11 75.3 35.6
12 78.4 43.1--------------------------------------------------------------------------------
So as you can see if a province has a 5% revolt chance per month, it is nearly 50% likely to revolt at least once in any given year. Each % increase from 1 -> 2 -> 3 is an extra 10% chance per year, quite significant. Above that the increment per monthly revolt % point drops quite a bit; so you can expect a noticeable change if you improve a province from 2% down to 1%, but you might not notice a drop from, say, 10% to 9%.
These numbers also apply to any other monthly % of course.