Current estimates of the neutral point and some conceptual notes
Comparing quality and quantity of life is a complex topic with important philosophical assumptions that apply not only to the wellbeing framework. You can see much more detail about this in our report “The Elephant in the Bednet” (Plant et al., 2022). This is a brief summary of the current literature on the neutral point.
Neutral point research
The neutral point, or the ‘0’ point where wellbeing is neither positive nor negative (often used as the equivalent of death or non-existence), is used to quantify the benefits of extending a life in WELLBYs (see more detail in the next section). It is also used as the lower point for the WELLBY valuation method where the value of a QALY is converted to WELLBYs (see the UK Treasury Green Book guidance).
There are some conceptual considerations (see next section), but this is also partly an empirical question. One approach to the neutral point has been to survey people about it. The Green Book cites the Peasgood finding of a neutral point of 2. However, there have been a few more studies since, and we think it is worth collecting them in one place and putting them forward (see Table 1).
We encourage people to cite these (or this report) and use these rather than the Peasgood finding for the following reasons: the Peasgood paper is not available anywhere, it uses a time trade-off methodology which might not be the most straightforward approach for a wellbeing framework, and it has a relatively small sample size.
The values vary widely from 0.56 to 6.05. Note that a WELLBY is a 1 point increase on a 0-10 wellbeing scale for 1 person for 1 year, so this indicates very substantial disagreement (more explanation below). This is often due to different methodologies where questions about neutrality in wellbeing generate higher responses than questions about “worth living” or death. The average of the literature is 2.82 (2.58 when weighted by sample size).
A lot more research is needed, and we hope that making the current findings more visible will boost new research and improve current usage. We recommend that people show how sensitive their results are to different values of the neutral point (e.g., our app for our evaluation of AMF). We recommend that new research be done across different methodologies and populations.
Table 1: Summary of the literature on the neutral point.
Source | Value | Method of elicitation / note | Sample |
Samuelsson et al. (2023) - A pilot survey by HLI | 1.26 | Asked when life is no longer worth living on a 0-10 life satisfaction scale. | N = 79, UK |
Samuelsson et al. (2023) - A pilot survey by HLI | 5.30 | Asked where the balance was between satisfied and dissatisfied on a 0-10 life satisfaction scale. | N = 128, UK |
Peasgood et al. (unpublished) | 2.00 | Time trade-offs. A QALY method rather than asking about a wellbeing scale. | N = 75, UK |
IDinsight Beneficiary Preferences Survey (2019, p. 92) | 0.56 | “at what point on the ladder from 0 to 10 is it worse than dying?” | N = 70, Ghana and Kenya |
Moss (unpublished survey by Rethink Priorities) | 2.49 | Asked at which level they would prefer to be alive rather than dead (converted from 0-100 to 0-10). An issue is that it mixes pain, suffering, unhappiness, pleasure, etc. in the scale. | N = 35, likely UK |
Moss (unpublished survey by Rethink Priorities) | 6.05 | Asked at which level is minimally acceptable to live an extra year (converted from 0-100 to 0-10). An issue is that it mixes pain, suffering, unhappiness, pleasure, etc. in the scale. | N = 101, likely UK |
Jamison et al. (yet-to-be-published survey) | 2.39 | Asked to compare policies that save people from dying (converted from 0-100 to 0-10). Mixes multiple definitions of wellbeing / best experience | N = 1800 (600 Brazil, 600 China, 600 UK) |
Jamison et al. (yet-to-be-published survey) | 2.54 | Asked to compare policies that save people from non-existence (converted from 0-100 to 0-10). Mixes multiple definitions of wellbeing / best experience | N = 1800 (600 Brazil, 600 China, 600 UK) |
Conceptual notes about the neutral point
Let’s start with how the benefits of extending life in WELLBYs are often calculated (expanding on Layard & Oparina, 2021):
Where:
- The effect is summed over the expected lifespan gained L for each time point t. For example, if an intervention saves someone’s life and they will go on to live 30 more years, the effect will be summed for each year t of L = 30.
- Wt represents the reported wellbeing of the individual at year t.
- The neutral point N represents where wellbeing goes from negative to positive on the wellbeing scale.
- G represents the grief spillover that is avoided for a certain number of non-recipients NR.
- δ is the discount rate, meant to capture fundamental uncertainty about the future.
So, to give a simple example, if someone would live another 30 years at 7/10 wellbeing, and the neutral point is 5/10, that would be 60 WELLBYs if we ignore the discounting and grief effects. If we slightly adjust the example given above, changing only N by setting it to 2 instead, we now find that saving the same life is worth (7 − 2) × 30 = 150 WELLBYs. It would be deemed 2.5 times as valuable, even though no fact of the matter has changed!
Conceptually, we do not want to set the neutral point either too high or too low. If it’s too high, we prioritise life-improving interventions at the expense of life-saving ones. If too low, the reverse problem emerges.
However, it is not obvious where, or how, to set the neutral point.
A natural thought is to set the neutral point at 5/10 on the life satisfaction scale (i.e., the middle of the scale), which would likely correspond to someone having a neutral level of wellbeing at that time (i.e., life is neither good nor bad). However, there are a substantial number of people worldwide whose life satisfaction is less than 5, and setting it here has the implication that extending their lives would be bad, as it would cause negative WELLBYs. Arguably, 5/10 is too high.
To avoid this problem, we might consider setting the neutral point at 0/10. But this has the implication that no life, even one of constant agony, could ever be bad – you cannot report being -1 on a 0-10 scale. Arguably, 0/10 is too low.
However, any particular choice between 0 and 5 is, arguably, ad hoc. 5/10 at least seems a principled choice, because it aligns the neutral point - death is neither good nor bad - with a zero level wellbeing - if wellbeing consist in life satisfaction, and someone is neither satisfied or dissatisfied, with life, then presumably their wellbeing is zero. Choosing a number between 0 and 5 has the appeal of avoiding ‘too far’ in either direction, but lacks a theoretical justification.
A further possibility, following the thinking above, is that there may be different neutral points (on a 0-10 scale) for different measures of wellbeing, based on the theoretical rationale for that measure. An obvious difference here is between happiness and life satisfaction.
If one is a hedonist about wellbeing, that is, wellbeing consists in happiness, then a life that is good for you, and so worth continuing, is one where you would be, on average, happy; vice versa for a bad life. If 5/10 on a happiness scale represents being neither happy nor unhappy overall, a life at an expected average of 5/10 would be neutral with respect to happiness, indicating a neutral point of 5/10 on happiness scales if one accepted hedonism.
If one accepts a life satisfaction view about wellbeing, where wellbeing consists in your overall judgement of your life, then there is greater theoretical scope to say that individuals get to decide for themselves the point at which their life is worth continuing; this is much like the life satisfaction view allows individuals to decide what makes their life go well in general. Hence, on the life satisfaction view, and using life satisfaction scales, it may be up to individuals to decide their neutral point.
What this line of thinking suggests is that there may not be a universal neutral point across all wellbeing scales and that efforts to determine it are appropriately ‘downstream’ of moral questions about what wellbeing is. It also plausibly suggests a way to reconcile the result that people say the neutral point on life satisfaction is not 5, but around 2. People may think 2/10 life satisfaction is the point at which their lives would be, in expectation, neutral for happiness.
In any case, given all these intricacies, one tempting way forward is to survey members of the public and take an average – although this is, arguably, more appropriate if one thinks life satisfaction, rather than happiness, is what matters.
Conducting such surveys is, however, not straightforward. One issue is that this is a complex topic, and so one would want to check whether respondents had properly understood the question. Another is that there are various specific questions one could ask to generate a number, and these can lead to widely different results, as demonstrated above.