This article deals with the concept of specialization and its measurement based on the concept of diversity and its evaluation through suitable indices of descriptive statistics. After a brief introduction on economic, sectoral and industrial specialization, a discussion of the concept of diversity in economics and the relationship between diversity, economic growth and stability is presented and then the idea of measuring economic specialization with the Gini’s index of mutability is proposed. A case study concerning Italian regional specialization represents the application to show the usefulness of the methodological proposal.