Quantifying Quality of Life

Abstract

The concept of quality of life (QoL) which is most relevant to medical and medicopolitical decisions is QoL as goodness of life, e.g., the value of a life for the person who lives it.

Mainly because of the interdependence of values, components of an individual human life cannot be ordered in such a way as to permit a complete and context-free ordinal scale. However, local orderings (given a set of fixed conditions) can often be found.

Similarly, although local ratio scaling of the desirability of life components using direct ratio estimation seems to be possible, the scales cannot be made complete.

Ratio scale values assigned by an individual to the goodness of life components by estimation need not always be even locally additive, since there may not exist any principle of composition.

By statistical means, representations of (something like) the value of life components have been derived, which are locally near-additive and which may be useful on a population basis (the QUALY methodology). They are however not useful on an individual basis, nor outside the proven domain of additivity.

The question whether the numbers representing the values of different lives can be added is wrongly put. There is no such thing as a composition of a supra-life from individual lives. The real question is whether the numbers should be added - whether the sum is the morally decisive arithmetical quantity to be calculated here. To this, utilitarianism answers Yes, while egalitarianism answers No.

The measurement part of QUALY methodology must be kept conceptually apart from utilitarian ethics.