How Do You Measure Whether
Life Is Going Well?

Objective versus Subjective — What is the Difference?

Objective indicators of quality of life are things that can be independently verified — income, employment status, the number of social contacts a person has, or a medical diagnosis. For decades, these were the standard tools used to assess how well rehabilitation was working.

Subjective quality of life is different. It refers to how an individual perceives and evaluates their own life. It cannot be assessed by an outside observer — only by the person themselves. This distinction matters enormously, because the relationship between objective circumstances and subjective experience is surprisingly weak.

Research consistently shows that objective measures — income, health status, housing — are poor predictors of whether a person reports feeling satisfied with their life. Two people in identical circumstances can rate their quality of life very differently, because what matters is not the circumstance itself but how the person interprets and values it.

A major advantage of subjective assessment is that it allows each person to evaluate their life according to their own values and priorities. This is essential when working across different cultures, age groups, and disability types — a lower standard of mobility may be entirely acceptable to one person and devastating to another.

How Satisfaction is Measured

The most commonly used approach in the SCI literature is to ask people to rate their satisfaction with specific areas of life on a numerical scale. This gives researchers a way to compare results across studies and against general population norms.

Satisfaction ratings work because the concept of satisfaction is widely understood. Most people have a clear sense of what it means to feel more or less satisfied with something in their life. This makes it possible to generate reliable, comparable data across a wide range of people.

How Many Scale Points?

One of the most important technical decisions in designing a satisfaction survey is how many points to include on the rating scale. Too few options — say, just three or four — and people cannot meaningfully distinguish between how they feel about different areas of their life. Too many and it becomes confusing and arbitrary.

Research by Cummins (1998) indicates that the optimal number is around ten scale points. This gives respondents the ability to express meaningful differences in satisfaction in approximately 10% increments — fine enough to detect real variation without overwhelming them with choices.

How Should the Scale be Worded?

The wording of the scale endpoints matters. If different respondents interpret the same label differently, the data becomes unreliable. The most robust approach is to use a bidimensional, end-defined scale — meaning the two extreme ends are defined with clear, opposite adjectives, such as 0 = completely dissatisfied and 10 = completely satisfied, with a neutral midpoint.

This approach gives the respondent the full range of human experience to choose from, rather than limiting them to positive responses only.

What the Research Showed — Scale Quality in the SCI Literature

As part of this research programme, the measurement instruments used across 41 published SCI studies were reviewed and evaluated against the criteria above. The findings revealed a significant weakness in the existing literature.

This finding has an important practical implication: the overall picture of life satisfaction after SCI presented in the literature may be somewhat worse than reality, because most studies used scales that were not sensitive enough to detect the full range of how people actually feel.

This is one reason why the Comprehensive Quality of Life Scale (ComQol; Cummins, 1997) was chosen for the primary study in this research programme. The ComQol uses an 11-point, bidirectional, end-defined scale — the closest available instrument to the theoretical ideal.

The table below summarises the instruments used across the 41 surveys examined, showing the wide variation in how quality of life was measured and the inconsistency in scale design that makes direct comparisons between studies difficult.

Table 1: Instruments used to measure subjective quality of life in surveys of the SCI population

Mean number of scale points across all instruments: 5.9. Only five surveys used an appropriate number of scale points (around 10). Scales with fewer points tend to produce deflated satisfaction scores by limiting the range of responses available to participants.

Why This Matters for Rehabilitation

The argument for subjective quality of life measurement is ultimately an argument for taking people seriously. Rehabilitation exists to help people live well — not just to restore measurable function. If we only measure function, we may be improving objective outcomes while missing whether the person actually feels better.

Furthermore, using a standardised instrument that applies equally to people with SCI and the general population means that the results can be compared. This prevents rehabilitation programmes from setting a lower bar for people with disability — measuring success against a diminished standard rather than against the full range of human flourishing.