I understand that in the espionage tab of the game, there are stars next to the your cities and that they refer to the potential that each city has. However, I have more cities with 5-star potential than the number of spies I have (I have 4 spies by the way). Thus, I would like to know how to calculate the chances of your cities' information to be stolen and eliminate the enemy spies that are camped in my cities.
Is there a way to calculate the chance of your cities information? For example, maybe via your cities population, the science, or maybe the difficulty of the game.
In case this matters, I am also using the Gods and Kings expansion pack and not the Brave New World expansion pack.