How is local city happiness calculated?

[Boombar]

I have -2 poverty, -2 crime, +10 from science, +1 culture and somehow my capital is at -3 happiness. Shouldn't it be something like +7? or am i missing something here?

 

[Legen]

The needs of a city only generate unhappiness from each of these four sources. Any excess in one source doesn't generate surplus happiness, nor compensate for negative values in the other sources.

So, your capital has 4 unhappiness from needs, and 1 happiness from some other source (social policies, certain beliefs, etc), for a total of -3 happiness.

 

[Enginseer]

"I may be very smart, but I may be robbed of my ever-decreasing wealth, we need barracks and markets."

This is a better system of happiness as you cannot neglect your cities and just specializing to compensate for its weaknesses(you can't just do that in real life!)