I understand that happiness affects growth? Does it matter to what degree my population is happy? Am I ok as long as I have one happy face, or is there a relative effect?
Also in Civipedia it says:
…a very unhappy population will also affect the fighting qualities of your armies as well.
How and when does it have an effect?
Here is a list of all the effects from happiness level that I could find. To answer your specific question, most of the effects care only if your civilization is happy or unhappy, by one 🙂 or :(. (I believe zero 🙂 is fine.) But there are three effects that care about the amount your civilization is happy or unhappy:
- VERY unhappy occurs when you hit -10 happiness. (Thank you @Oak)
- Golden Age points accumulate (or deplete) equal to the amount your civilization is happy (or unhappy)
- Piety->Mandate of Heaven uses your exact excess happyness to calculate how much culture you get.
Full list of effects:
- Growth: Cities grow normally.
- Golden Ages: If you have excess happiness, each turn it accumulates into Golden Age points, and when you have enough, your civilization enters a Golden Age. After the golden age the process starts again, although I believe you need more Golden Age points for each subsequent Golden Age.
- Growth: Cities grow at 1/4 speed when your population is unhappy.
- Golden Ages: The amout your civilization is unhappy is subtracted from the Golden Age points.
- Growth: Cities do not grow.
- Units: Settlers may not be trained.
- Production: Cities generate -50% production.
- Unit are less effective in combat. They get -33% combat strength.
VERY VERY unhappy (-20 or lower)
- Rebels will spawn in your border and attack your city
- Piety->Mandate of Heaven allows you to add 50% of your excess happiness to your culture each turn.
- Rationalism->Sovereignty boosts science +15% when your empire is happy.
- There are numerous social policies that affect the happiness level, but these are the ones that get effect from the happiness level.
- General info: mousing over the happiness listing on the top bar, left side, during various happy states.
- Golden age info: mousing over the golden age display on the top bar, left side, during various happy states.
- Combat info: Comparing happy (normal) combat strength to VERY unhappy combat strength, by mousing over an enemy unit. The VERY unhappy combat modifier is clearly listed in the calculations.
- Production info: mousing over a city’s production listing in the top left when VERY unhappy.
- Social Policy info: The social policy screen, accessible by clicking on the culture listing on the top bar, left side.
Source : Link , Question Author : Dan , Answer Author : Halfwarr