Chapter Eight of Life, Liberty and the Pursuit of Utility explores subjective wellbeing polls ("taking your life as a whole, would you rate yourself very happy, somewhat happy, or not happy at all?"). Those who say they are happy smile more than the average person, appear happier to friends and family, have higher self-esteem, are comparatively infrequent visitors to psychotherapists and are less likely to commit suicide. They have higher than average levels of activity in the left prefrontal region in the brain,which is rich in receptors for the neurotransmitter dopamine, and they register considerably lower levels of cortisol, an adrenal hormone related to the risk of obesity, hypertension and autoimmune conditions.
At the same time, subjectively happy people tend (weakly) to share a set of life circumstances: they are more likely to be married, employed, religious and relatively rich. They are also more likely to be found in countries where people trust the police and their governments. On the other hand, absolute (as opposed to relative) income doesn't seem to matter much at all. This finding appears to hold in middle income countries, but not amongst poorer people in poor countries.
When people face a lack of income sufficient to support the basics of welfare, then, they are less content. But once income becomes a status marker, the income that matters is relative, not absolute. And this happens pretty early on in the process of development. For example, real incomes per capita in China increased by a factor of 2.5 between 1994-2005, and this was associated with rapid increases in the ownership of goods—color television ownership increased from 40 to 82 percent of households, telephones from 10 to 63 percent, for example. Incomes started at a very low level, averaging $2,604 per capita. Nonetheless, the percentage of people satisfied with life declined.
The subjective happiness literature suggests that nonpecunary goods such as insurance and leisure are not viewed purely in relative terms, so that we should focus on increasing the supply of these goods rather than income.
At the same time, there are limits to the policy relevance of subjective wellbeing. The majority of variation in subjective wellbeing between people appears to be related to genetic factors rather than objective circumstances. Because of this, people lose little long-term contentment even as a result of catastrophic events that we may still want to minimize (accidents that lead to paraplegia, for example). Furthermore, what little varaition we can correlate with factors such as unemployment and poverty may be related to reverse-causation. Finally, the finding that having children has no impact on subjective happiness suggests that contentment lacks (even) as a overarching motivational force.