According to Professor Bjornskov, there are a number of basic universal factors that contribute to a nation's happiness: a democratic political system, a certain level of national prosperity, a functioning judicial system, and the absence of war. He estimates that thirty to forty countries meet these criteria. Once this foundation is in place, other factors influence the level of happiness, in particular trust in others and the freedom (or possibility) to choose one's own way in life.
--Happy as a Dane (2017)