According to the 2015 World Happiness Report, Iceland, Denmark, and Norway are the world's happiest countries, right behind Switzerland.
This may not be surprising to most considering Norway, for example, is the most prosperous country in the world. However, economic standing was only one of many factors used to assess people's happiness in this study.
What makes our Nordic countries (referred to as Scandinavian countries by the rest of the world) stand out, however, seems to be the very social fabric of our society, where communities are encouraged to thrive as a whole, and where governments actually have the best interest of its people in mind, in contrast to promoting individualism and unrestricted capitalism at the expense of the general good.
This is referred to the Law of Jante, a sociological concept in Nordic countries to describe a negative attitude towards individuality and success, to emphasize instead collective efforts.
Vikings have been living in tribes and communities for over a millennium, and to this day, it seems to be the right approach to live a happy life.