Disability Weight

A value between zero and one representing the severity of health loss from a specific non-fatal condition, used to calculate years lived with disability.

Source: Salomon et al. 2012

Current weights come from population surveys presenting lay descriptions of health states and asking respondents which of two described people is healthier. These paired comparisons are collected across large samples and combined statistically into a cardinal scale running from zero for full health to one for a state equivalent to death. Earlier rounds used expert panels and person trade-off exercises with small groups of health professionals, which drew criticism for reflecting professional rather than public judgement. The move to population surveys across many countries, and the finding that judgements were broadly consistent between them, is what supports applying one set of weights globally.

Source: Salomon et al. 2012

It measures the severity of a health state relative to full health, and nothing else. It does not incorporate how long the state lasts, which enters the calculation separately as duration. It does not reflect the value of the person's life, their age, or their circumstances. And it describes the state rather than the person, so two people with the same condition carry the same weight regardless of how they experience it or what support they have.

Source: Murray 1994

People living with a condition consistently rate it less severely than members of the general population imagining it, a pattern observed across many conditions and attributed partly to adaptation and partly to the difficulty of imagining an unfamiliar state. Using general population judgements is defended on the ground that the public bears the opportunity cost of what is funded. Using patient judgements is defended on the ground that they know what the state is actually like. The choice determines which conditions appear most burdensome and is not resolved.

Source: healtheconomics.wiki

The scales run in opposite directions, with zero representing full health for a disability weight and death for a utility. Disability weights come from comparative judgements about which described person is healthier, whereas utilities come from trade-offs involving time or risk, which require respondents to give something up. Utilities can take negative values for states judged worse than death, while disability weights are bounded at one. The two are not interchangeable despite the apparent symmetry of subtracting one from the other.

Source: Salomon et al. 2012

That respondents judge states they have never experienced, so the weights encode imagination rather than experience. That the descriptions are necessarily brief, so states differing in ways that matter clinically receive the same weight. That applying a single global set assumes severity is judged identically everywhere, which the consistency findings support only within the range of settings surveyed. And that the weights have been revised substantially between rounds, so burden estimates either side of a revision cannot be compared as though they measured the same thing.

Source: Anand & Hanson 1997