Nice to see that multiple factors are suggested and not just one magic bullet.
http://sciencenordic.com/how-happiness-challenging-gdp-measure-countrys-health
OPINION: Denmark has reclaimed its place as the happiest country in the world, according to the latest annual World Happiness Report, closely followed by Iceland, Norway, and Finland. But it is equality and not GDP that makes the Nordic countries top in the happiness polls.
The nations that top the usual measure of a countrys health its Gross Domestic Product, or GDP, which shows overall economic output were much lower down. The
US came 13th, the UK 23rd and China 83rd. This goes to show that GDP is by no means a conclusive measure of well-being and the report reflects moves to recognise this. In fact,
the report found a strong correlation between inequality and unhappiness.
The cluster of high performing Nordic countries at the top of the World Happiness Report suggests that there are shared features of policy and perhaps geography and culture that matter. These are countries where high taxes are used to generate relatively equal societies where social mobility and income security are much greater as a result. These countries tend also to have rather homogenous societies and the evidence is that in many situations people prefer being with others like themselves.
Meanwhile, at the bottom of the list are a variety of countries which are less homogenous but nonetheless either war-torn, close to being destitute and in the case of Burundi which comes bottom both.
More at link