Anyway, let's move on to the topic of revolts. A revolt in a city can occur if the owner of the city and the person who would own the underlying square if there were no city are different. In other words, a city might revolt if a neighboring city belonging to a different civilization has it within its cultural radius and that civilization's plot culture under the city is greater than the city's owner and that of all other civilizations with a city in range. You don't have to have a majority, you just have to have more of your nationality than the other guy. If a revolt can occur, there is a flat 10% chance each turn of making a revolt check.
During a revolt check, a random number between 0 and the city's revolt power is compared with the garrison strength. If the number is greater than the garrison strength, the city revolts.