As they mention in the end of the article - most Danes think they're in the best possible place in the world and have the best life you can get. I guess that is being happy? Surely you can argue whether it's factually true - but if you think you are happy - aren't you? :-)
> It's easy to seem the best if you keep your views parochial enough.
Or have some experience of the world outside the U.S. I think I live in the best possible place in the world. I don't begrudge Danes or Swedes for thinking the same. It's all heaven compared to Bangladesh.