I noticed odd behavior in this area as well.
First of all, what is the difference between approval (the value on the screen) and morale (the value you get when you hover the mouse over it)? They are nearly the same most of the time, but sometimes they differ a lot (like 20%). Also, the 30% morale from the multimedia center never actually occured in my game, no matter on which planet I tried it. Once approval (and morale) went up by 23%, once by 50%(that was with a 100% approval bonus on the tile) and so one. Never the full 30%. I guess there's some other factor involved, but I don't know which one.
While the tendencies of all the bonus and production values seem correct, the values themselves are never correct (well, correct with respect to what I expect them to be
) and that's a little frustrating, I have to say. I'd like a complete rundown of what factors into all this.