Can someone explain "hapiness from difficulty level" for me?

[omiman]

I have 6 cities. I sold Addis Ababa to Spain and my hapiness from difficulty level went up from 9 to 21. the nest turn it went back to 9. How is it calculated?

 

[Vortok]

It might've just been a tooltip error if that number itself changed. If your total happiness fluctuated it could've been a combination of factors.

The happiness from difficulty level is just a static, base happiness amount, depending on the difficulty that you're playing on. The lower difficulties (1-3) have a larger amount to serve as a bigger buffer.

 

[beetle]

Happiness can vary wildly from turn to turn. Absent screen shots or save files, my best guess is that by giving Spain such a nice city, you let her bump up a level in Tourism influence over you. At what point in the game are you? Are you post ideologies, and is Spain running a different ideology than you? Tourism influence happens in tiers, and moving from one tier to the next frequently has dramatic effect! You can watch for it coming, by checking the influence screen often, but there is not much you can do to stop it -- since it builds slowly but surely.

Out of curiosity, what did you get for Addis Ababa? Did you shop it around before accepting Isabella's offer? Even at lower difficulty levels, I would expect to net 3K at least!