How happy are people relative to neutral (as measured by experience sampling)? Most studies on experience sampling are about whether some activity correlates with increased or decreased happiness/subjective well-being. However, it's often hard to tell from these studies what number corresponds a neutral point, where someone is neither unhappy or happy (or equally so), or is feeling an valence/affect equivalent to a nonconscious state. For instance Experience Sampling Method: Measuring the Quality of Everyday Life (2007) shows its results in terms of z-scores, which are defined relative to some average, but it's unclear whether that average would be higher or lower than a neutral point. As such, while we can say that these people are happier in this situation than another, it's hard to see whether they're overall happy or unhappy in that situation.

I'm not particularly interested in what activities or age or gender correlates with happiness, but just how happy people are relative to some clearly defined neutral point. Ideally, the study wouldn't just show some average among all study participants across all their experiences, but also what percentile corresponds to what happiness ratings, and the range of happiness scores and the frequency of different happiness ratings for each person. Is there a study that addresses this topic?
I just finished reading this article (2018) by Michael Plant, a PhD student at Oxford University.  Given that it is not a peer-reviewed paper, it would be worth checking his references, but this is what he says about the neutral point:


  Life satisfaction surveys don’t ask people to specify what point on
  the 0 to 10 scale they would consider equivalent to not being alive. 0
  is labelled not at all’ and 10 ‘completely satisfied’. ... How could
  we settle where the neutral point is? Two strategies seem possible.
  First, we could find out at what LS scores individuals report their
  lives are neutral on experience measures of SWB. Second, we could poll
  people to ask at what LS score out of 10 they would be indifferent
  between living with that score for the rest of their life or dying. I
  am unaware of any analysis which has been conducted along either
  lines. Thus, for the moment, this unfortunately remains a point of
  armchair conjecture.


Note: LS = Life Satisfaction; SWB = Subjective Well-Being.