In 2005, a team of U.S. researchers developed a comprehensive model of sustainable happiness change that integrated the major lines of the subjective well-being literature. The result was a theory which proposed that up to 50 per cent of one’s happiness was rooted in a genetically determined set-point, 10 per cent was related to circumstantial factors (nation of residence, demographics, culture, income, etc), and the remaining 40 per cent was determined by intentional activities such as pursuing goals, looking at things optimistically, and being physically active.

-Research Digest Blog