Inequalities in self-reported health: validation of a new approach to measurement

This paper assesses the internal validity of using the McMaster 'Health Utility Index Mark III' (HUI) to scale the responses on the typical self-assessed health (SAH) question, "how do you rate your health status in general?" It compares alternative procedures to impose cardinality on the ordinal responses. These include OLS, ordered probit and interval regression approaches. The cardinal measures of health are used to compute and to decompose concentration indices for income-related inequality in health. These results are validated by comparison with the individual variation in the 'benchmark' HUI responses obtained from the Canadian 'National Population Health Survey 1994-1995'. The interval regression approach, which exploits a mapping from the empirical distribution function (EDF) of HUI into SAH, outperforms the other approaches. In addition, we show how the method can be extended to allow for differences in SAH thresholds across different groups of people and to measuring and decomposing 'pure' health inequality.