The SPI is composed of 3 dimensions, each of which is given a score baed on a basket of measures from reputable sources such as the WHO. The dimensions have some passing resemblance to Maslow’s hierarchy; Basic Needs, Wellbring and Opportunity. Porter and his colleagues have worked hard to make sure the dimensions are (i) internally consistent and (ii) based on both globally available and reputable data.
In the SPI, no dimension (or measure) is given priority – nevertheless, the choice of dimensions (and measures, to a lesser extent) cannot help to be subjectice and reflects the bias/preference/worldview of the author. SPI for example is very much based on human needs and less so on ecological balance (though it is included as one of the aspects of wellbeing)
An alternative measure, the ‘Happy Planet Index’ can be usefully compared to SPI. The two measures give very different results – the SPI winner is Sweden and the HPI winner Costa Rica. At least at the time of writing. Two countries I have yet to visit. (now – how to do so without wrecking the planet….. )