Fractionalization indices measure the odds two random citizens differ by group.

Evidence

In all cases the index of fractionalization is computed (as it is standard in the literature) as the probability that two randomly drawn individuals form the population of the country belong to two different groups. — Philippe Aghion, Alberto Alesina, and Francesco Trebbi, Endogenous Political Institutions, 163

Categorization

• DEFINE: Gives the precise standard construction of a fractionalization index as a pairwise dissimilarity probability.
• CANDY: ‘Your country’s diversity score is literally the chance two random strangers are from different groups’ — an easy elevator version of a technical index.