Im from south Europe where in my opinion we are quite happy, but at the same time we love to complain. Its just cultural, it doesnt mean that we hate our lifes, we just like to be negative some times :) I lived as well in a few countries of that list and I cannot say they are happier. I think they act happier.
Answering a "How are you today?" question differs among countries
In some countries people answer "awesome, and you?" and perhaps he/she just broke up with the couple.
In some other countries you would answe "Man, I feel so unlucky and terrible" but actually you just won lottery but rather than a million you got few thousand euros :)
just cultural... :)