Incorporating Natural Growth and Net Migration in a Composite Fuzzy Index for Depopulation: Italian Municipalities as a Case Study

Traditionally, depopulation processes are analysed by classifying territories as “declining” or “not declining”. This study moves beyond that binary approach by adopting a fuzzy methodology. The objective is to extend the Composite Fuzzy Demographic Index (CFDI), originally based on a single demographic variable, in order to break down depopulation into its two main components: natural growth and net migration. Using annual data on the resident population in Italian municipalities between 1991 and 2024, two distinct CFDIs are calculated. The resulting values then serve as coordinates in a Cartesian plane, making it possible to distinguish and analyze the relative impact of the two components on local demographic dynamics.