The UN just released their third ever Word Happiness Report. Vox reports a striking finding, GDP per capita is one of the most important variables for determining national happiness. As the map shows, the happiest countries (darkest blue) are also some of the world's wealthiest. Social support, healthy life expectancy, freedom, generosity, government corruption were also indicative of national levels of happiness.
The most striking thing about the map is that people rich countries are, overall, considerably more satisfied with their lives than people in poor countries. That shouldn't be surprising. The weight of the evidence suggests that both momentary happiness and life satisfaction are heavily correlated with GDP per capita.