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CHAPTER 1.5. MEASURING QUALITY OF LIFE

5.1 This section aims to give a broad overview of different approaches to measuring Quality of Life ( QOL) and the main methodological debates. How QOL is measured clearly relates to how the term is defined, and therefore to what is being measured. As we have discovered when people say they are measuring QOL, they may, in fact, be seeking to measure quite different things, to quite different ends. ¹⁵¹ The types of measures developed and the position taken on methodological issues therefore vary between different disciplines according to their objectives and philosophical outlook. As we shall see below, the key issues surrounding the measurement of QOL therefore closely relate to the key debates over definitions.

5.2 A helpful methodological overview is provided by Schalock (summarised in Table 5.1 below). ¹⁵² While he is concerned with measuring the QOL of people with intellectual disabilities, the principles he outlines have a wider relevance. Schalock advocates a "pluralist" methodological approach because it addresses the multidimensional nature of QOL, and acknowledges that the different dimensions of QOL may best be measured by using a range of techniques. Thus QOL may be measured, simultaneously, from both subjective and objective perspectives, including both subjective and objective assessments of objective factors. The combination of multiple research approaches to the same research subject, known as "triangulation", overcomes some of the weaknesses and problems of individual research methods, producing stronger research findings.

Table 5.1. Methodological pluralism applied to Quality of Life measurement

Source: Schalock (2004), p. 207.

5.3 We can make a broad distinction between methods used to measure the QOL of the general population, and those used to measure the QOL of individuals. In both approaches the dominant research methodology can be described as positivist and based on quantitative methods. Qualitative methods are used in QOL research, particularly in the development of QOL instruments, but more in some disciplines than in others. They are less likely to be found in social indicators field, and more likely to be found in disabilities or psychology research, where observational techniques are often used in tandem with measurement instruments.

• QOL of populations - based on the "social indicators" tradition. This usually involves the identification of indicators and measures relating to a range of QOL dimensions/domains. Often these are aggregated to construct a single index of QOL. These indicators may be both objective and subjective, drawn from socio-economic statistical data collected by governments and/or survey data. Standard sources of international data used to construct indices of this type are the World Bank's World Development Report and the United Nations Compendium of Social Statistics and Indicators. One example is the Human Development Index, designed to compare the QOL of nations, which covers per capita income, education and health variables. ¹⁵³
• QOL of individuals - While other techniques are found, including ethnographic studies, and observation of behaviour, the dominant approach measures QOL using some form of self-assessment instrument, i.e. a questionnaire. This is the case for each of the first two of Schalock's types of "measurement focus": personal appraisal and functional assessment.
• There are now literally hundreds of different instruments of this type: within the field of health-related QOL alone there are general measures of QOL and hundreds of disease-specific measures. ¹⁵⁴ There are also masses of reviews comparing instruments, assessing their respective strengths and weaknesses, and identifying and discussing methodological issues. ¹⁵⁵ These instruments can vary considerably in design and Haas helpfully describes 3 three main approaches, each of which presents methodological issues relating to measurement: ¹⁵⁶

• Uni-dimensional single scale measures ¹⁵⁷: these are "global QOL" measures using a single question, rating or item to measure a concept. Most commonly in QOL studies, individuals are asked to rate their satisfaction with life as a whole, or their overall well-being. These are fairly blunt instruments that confuse QOL with other related concepts.
• Multi-dimensional, single-scale measures: these break down QOL into its various dimensions or domains and use a single question, rating or item to measure each one.
• Multiple separate scales: these use a number of separate scales each measuring individual dimensions of QOL, for example satisfaction, self-esteem or social relationships. Each scale comprises a "battery" of questions, the scores of which may be aggregated and weighted to give an overall measure for each dimension.

Measurement issues

5.4 Whether the assessment is at the individual or general population level, there are a number of common measurement issues.

• Identification of dimensions/domains. As already noted, the search for the definitive set of "core" QOL domains has produced widely varying results, although with some areas of consensus. Summarising a range of about 60 QOL instruments used in medicine, Birnbacher says:

"these differ both in the dimensions in which QOL is measured and in the weight they give to these dimensions in aggregation. Most measures take into account 3 core dimensions of QOL: the physical, the psychological and the social dimension… In detail, there are many differences, both in the number of dimensions, the distribution of items among them and the weights assigned to individual items". ¹⁵⁸

• Some degree of subjective judgement is involved in domain selection. For example, the WHOQOL Group has been criticised for its decision to have six QOL domains, with no justification or rationale for either this choice of number, or for the omission of other domains found in most prior QOL scales, such as material well-being or productivity/employment. ¹⁵⁹
• An alternative approach is to investigate individuals' views about the things that contribute to their QOL, and derive QOL domains through this process. ¹⁶⁰ Rapley describes this approach, involving subjects as participants, as "emancipatory" contrasting it with "mainstream" QOL research which imposes QOL models on individuals in a potentially "oppressive" and "disempowering" manner. ¹⁶¹ As Day and Jankey state,

"When researchers impose the domains of life to be measured, they risk omitting important aspects that may have greater relevance to that person or imposing aspects that have little or no relevance. The results, therefore, may have little validity". ¹⁶²

• And finally, as we shall see later on, many researchers choose to operationalise QOL in terms of one aspect of QOL - for example, life satisfaction - presenting this as a measure of QOL as a whole. This is often not acknowledged or discussed, with the result that studies that purport to look at QOL are in fact examining one dimension of a much broader concept. ¹⁶³ Bowling does not recommend single item measures on the basis that a single question is unlikely to "effectively tap a given phenomenon", and argues for scales to be used in preference. ¹⁶⁴
• Selection of indicators - the same type of issues apply here. These are often selected, for pragmatic reasons, driven by data availability and not theory, and inevitably subjective decisions are involved in the process of selection, and in determining exactly what should be "counted" for use. ¹⁶⁵

For example, reviewing the existing indices of national QOL, which use a social indicators approach, Diener laments the "unsystematic and atheoretical manner" in which variables have been selected for inclusion, with the result that different indices produce quite different results. He highlights the absence of any accepted, systematic method for selecting both QOL dimensions and indicators, and he attempts to rectify this. ¹⁶⁶ In his view indicators should be selected either on the basis of common universal values (for cross-national comparisons of QOL) or in relation to the culturally specific values of an individual nation (for a single nation study). ¹⁶⁷

• Subjective - objective debate. As writers differ on what they are trying to measure, therefore so do their methods. They may be trying to measure (a) solely a subjective perception of the external conditions of QOL, (b) subjective perception balanced against objective indicators, (c) subjective perception and objective indicators combined into a single index of QOL, or (d) solely objective indicators of external conditions of life. The divergence of opinion on these issues has been documented above. The most common critique is that social indicators may be good objective measures, but tell us little about how individuals actually feel about their lives. Whereas on the other hand, subjective measures of people's objective conditions are likely to be affected by their temperament and social expectations and may not provide a reliable indication of their actual circumstances. For this reason, Diener and Suh advocate the combined use of social indicator and subjective well-being measures. As the limitations of each type are different, they argue that,

"they provide alternative views of societal quality that are unlikely to be affected by common errors of measurement". ¹⁶⁸

Similarly, Schalock (1996) argues for a core set of QOL dimensions with both objective and subjective aspects - i.e. each dimension may lend itself to either subjective or objective assessment. ¹⁶⁹ The advantage of this approach is it breaks down a rather false dichotomy between objective and subjective approaches.

• Weighting of QOL domains or indicators. Decisions about the weighting of indicators can have a huge effect on research outcomes. Methods of weighting variables are therefore of great importance and the subject of much debate. ¹⁷⁰ For example, in a study of the QOL of over 300 city areas in the US, the authors found that, according to the weightings given to particular variables, 134 cities could be ranked first and 150 different cities could be ranked last. ¹⁷¹

Writers who acknowledge the importance of personal values to QOL agree that QOL domains should be weighted to reflect the relative importance that individuals place on each domain. ¹⁷² Felce and Perry argue that value-based weighting be applied to both subjective and objective measurements, while Cummins says that only the subjective measures should be weighted because the objective measures must be "primarily normative indicators of well-being" ie referenced to norms within the general population. ¹⁷³ In his view it is important to be able to compare normatively linked objective measures with value weighted subjective measures, rather than combine them into one overall index of QOL.

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