Perception index

A well-made number that measures belief rather than incidence. The clearest example in this course is Transparency International’s Corruption Perceptions Index, which aggregates assessments by experts and businesspeople of how corrupt a country’s public sector is thought to be.

It tells you something true about reputation. It does not count a single stolen peso, and it cannot, because nobody has that count. Any lesson or script that uses it says so in the same breath, every time.

The failure mode this term exists to prevent is a sentence like “the index shows corruption rose.” What rose was the assessment. Whether the underlying incidence rose is a separate question that needs prosecutions, audits or budget records to answer.

Source: The instrument is Transparency International’s, published annually with a public methodology, https://www.transparency.org/en/cpi . The handling rule is this course’s own, carried from its citation discipline: perception versus incidence is named every time it applies.

First used in: 0.2 · How we will know what is true