According to the "World Happiness Report", the happiest people in the world live in Denmark, Finland and Norway. The report is published by the United Nations (the first edition was in 2012).
According to one of the people interviewed, it's all an expectations game: "We don't expect much from life in Denmark, and we are happily surprised when something goods happens." (quote from memory). I doubt that it is that simple. Here is the Deutsche Welle video:
The top 10 happiest nations on the planet are:
8. New Zealand
Happier countries tend to be richer countries. Over time as living standards have risen, happiness has increased in some countries, but not in others (like for example, the United States). On average, the world has become a little happier in the last 30 years (by 0.14 times the standard deviation of happiness around the world).
Stable family life and enduring marriages are important for the happiness of parents and children. In advanced countries, women are happier than men, while the position in poorer countries is mixed.
Happiness is lowest in middle age.
First World Happiness Report Launched at the United Nations - The Earth Institute - Columbia University http://bit.ly/ZdgyAr