Slitherine

i would like to know that just how many factors affect the happiness
for example,
1.garrison factor is clear, it depends on the units garrisoned.
2.overcrowding factor: does it decrease on moving people to other cities? logic says it should.
3.building effect is clear. does epic buildings like the colloseus have empire-wide effects of just on the city where it is built?
4. empire effects: it depends of the tax levels etc and the no. of resting workers. any other factors? like newly conquered cities being less happy than older ones? and does the presence of barbarians and pirates around a city cause a dip it happiness?

It's tough to remember for sure how it works, but nearby pirates & raiders don't effect happiness. I don't remember if newly captured cities have a happpiness penalty or not & can't remember what the effect of sieges is - hopefully it is all explained in the manual! You can also have a look at the data files to see what variables are set - see the tweaks.txt file in the data directory. This gives clues as to what is effected and also lets you change them if you like.

Reducing overcrowding/population does improve happiness. One thing not mentioned is the events - events can modify happiness significantly.

Larger empires get happiness penalties in all cities. You can also set the food rate higher to improve happiness.