Migration as a diffusion process: the case of Bologna municipality.

Introduction and Theoretical Framework - The demographic change is currently taking place, characterized by depopulation in certain areas due to phenomena such as population aging, emigration, and declining fertility rates. Italy is a clear representative of this reality, as measurements and projections from the Italian National Institute of Statistics indicate a progressive decline in population throughout the country (ISTAT, 2023). In this context, it is interesting to understand why this phenomenon is also present in the northern region of the country, which is highly industrialized, with high levels of quality of life and higher per capita income. According to official predictions, while the northern part of the country does not show as rapid a decline as the central and southern regions of Italy, it is still projected to reduce its population by 2.7 million inhabitants (ISTAT, 2023). In this regard, we are interested in understanding the depopulation phenomenon, with a special focus on emigration from municipalities with high standards of living, such as the municipality of Bologna. Bologna is the seventh most populous municipality in Italy with about 392,800 residents as of Dec. 31, 2022. Among the features worth mentioning is that Bologna confirms itself as an attractive city, as shown by the migration balance, particularly active with the South and the Islands and with foreign countries. 44 percent of immigrants in Bologna are between the ages of 25 to 34 years old and, among them, more than 80 percent are Italian (Comune di Bologna, 2021). To study the emigration flow of the inhabitants of Bologna, the diffusionist paradigm was used, which has been widely utilized in marketing but has also been applied in various fields of research (Rogers, 2003). For this analysis, in a first stage, emigration from Bologna was examined through the Bass diffusion model (Bass, 1969). According to this model, in a market analysis context, the diffusion of new behaviours is driven by two types of communication: external, which includes advertising and public awareness campaigns, and internal, which includes social influence, word-of-mouth, and imitation. These two factors give rise to two categories of adopters: innovators, who are primarily receptive to external sources of information, and imitators, who adopt in response to interactions with earlier adopters (Bass, 1969). 2 As second step, the analysis was complemented with a more structuralist approach (Palloni, 2001), by estimating regression models to address the association of innovation and imitation coefficients derived from the Bass model with sociodemographic and socioeconomic variables. Regarding the latter, the study focused on the economic conditions of the selected destination, allowing us to elucidate whether factors such as unemployment rate, median income, or property values are determinants in the decision to migrate.