Well-Being is a sum of various parts. The parts vary according to who's talking or writing. For some, well-being is as simple as happiness, an experiential state characterized by positive emotion. For others, well-being is composed of multiple features, some of which may reduce happiness. In the case of the latter approach, a single metric for well-being is pretty meaningless.
Speaking of which, consider "meaningfulness", or sense of purpose and value. Want to have a meaningful life? Well, you may have to give up some happiness. Here's a brief summary of some research on the matter:
"Happiness was largely present oriented, whereas meaningfulness involves integrating past, present, and future. For example, thinking about future and past was associated with high meaningfulness but low happiness. Happiness was linked to being a taker rather than a giver, whereas meaningfulness went with being a giver rather than a taker. Higher levels of worry, stress, and anxiety were linked to higher meaningfulness but lower happiness." - Baumeister, Vohs, et al. (2013). "Some key differences between a happy life and a meaningful life."
And then there's "life satisfaction", which reflects an evaluation of one’s life as a whole. There is some overlap between life satisfaction and other conceptions of well-being but only some. Consider "flourishing", a popular take on well-being. One study found that a third of flourishing people were not characterized by high life satisfaction and half of those with high life satisfaction did not meet criteria for flourishing.
What's flourishing? A composite measure of well-being, of which there are several variations. Here's one:
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References:
Baumeister, R. F., K. D. Vohs, et al. (2013). "Some key differences between a happy life and a meaningful life." The Journal of Positive Psychology 8(6): 505-516.
Huppert, F. A., & So, T. (2009). What percentage of people in Europe are flourishing and what characterises them? Briefing document for the OECD/ISQOLS meeting “Measuring subjective well-being: an opportunity for NSOs?” 23/24 July, 2009, Florence, Italy.
Huppert, F. A. and T. T. C. So (2013). "Flourishing Across Europe: Application of a New Conceptual Framework for Defining Well-Being." Social Indicators Research 110(3): 837-861. https://link.springer.com/article/10.1007/s11205-011-9966-7