I am wondering what determines whether or not a city will go into civil disorder due to unhappy citizens? Sometimes i can have six happy and four unhappy and be fine, yet that is normally due to overcrowding, yet in my border cities i have three happy and one unhappy, and wam civil disorder? I figured it was a percentage of the pop but that does not seem to be correct, is it due to the severity of unhappiness, i suppose that forced labor is worse than overcrowding, but i am looking for some confirmation.