First, I’ll upend a possible misunderstanding: My point here is not that “so many things in life cannot be measured.” I agree with that statement but not with the abdication surrounding it. It is exquisitely difficult to measure certain things, such as happiness, but I see reason to peer into the difficulty. Through trying and failing to measure happiness, we can learn more about what it is.
Lately I have seen quite a few studies that include a happiness rating: the study I discussed here, a study that Drake Baer discussed just the other day, and a study that Andrew Gelman mentioned briefly. In all three, the respondents were asked to rate their happiness; in none of them was happiness defined.
Some people may equate happiness with pleasure, others with contentment, others with meaning. Some, when asked about their happiness level, will think of the moment; others, of the week; still others, of the longer term. The complexities continue; most of us are happier in some ways than in others, so how do we weigh the different parts? The weights could change even over the course of a day, depending on what comes into focus. Happiness changes in retrospect, too.
In addition, two people with similar “happiness levels” (that is, who would describe their pleasure, contentment, and meaningful pursuits similarly) might choose different happiness ratings. A person with an exuberant personality might choose a higher rating than someone more subdued, or vice versa.
Given the extraordinary complexity of measuring happiness, I distrust any study that measures it crudely and does not try to define it. I doubt that it can be defined or measured exactly; but a little more precision would be both helpful and interesting.
Incidentally, the search for precision can bridge the humanities and the sciences; while they will always have different methodologies (and even different questions), they have a common quest for the right words.