Forgot to ask this as well.

[Andres]

On the other hand, squalor can be your best friend, especially in very crowdy cities which tend to become more and more difficult to keep under control.

If the squalor is high, it can lead to the plague which will reduce your population significantly. Once the plague is over, it will be much easier to control the city again. If you have a spy in the infested city, you can move him to a) the enemy cities or b) your other over-crowded and therefore difficult to control cities to cause the plague in those settlements



Just make sure you keep your valuable named characters (good generals) away from the plague.