This paper studies a famous unsolved puzzle in quantitative social science. Why do some nations report such high levels of mental well-being? Denmark, for instance, regularly tops the league table of rich countries' happiness; Britain and the US enter further down; some nations do unexpectedly...

The paper provides evidence that happiness raises productivity. In Experiment 1, a randomized trial is designed. Some subjects have their happiness levels increased, while those in a control group do not. Treated subjects have 12% greater productivity in a paid piece-rate Niederle-Vesterlund...