Demographic projections aim to study the probable future of a population in terms of total size and structural components. This kind of product is used among policy-makers both as a knowledge tool for assessing population aging trends, and as a source for developing further forecasting models. The possible uses of the projections are in fact many and vary from health planning to social security, from the study of urban planning needs to the energy-environmental ones, from the organization of school facilities to the transport network.
With the “Demographic projections” project, included in the National Statistical Program (PSN code IST-01448), Istat has been responding to this kind of needs for over thirty years, with a frequency that in the past was periodic (every three-five years). Since 2017 the frequency of release has become annual. Furthermore, from the original deterministic approach the model has been transformed into probabilistic.
The interest in the territorial dimension has always characterized the activity in the sector of demographic projections, because the possibility of producing detailed territorial information is essential for analyzing and understanding the national demography itself. However, the regional level of detail is often insufficient because the planning of a territory increasingly needs micro-founded information. The impulse of this growing interest has therefore led Istat to develop demographic projections at municipal level, a product of an experimental nature for the time being. After the first edition released in 2021, which concerned municipal projections based on 1 January 2020 and up to 2030, the update released in 2022 covers the time horizon 2021-2031. The updates concern the replacement of the population in the base year with the latest one made available by the Census (on January 1st 2021) and a partial review of the evolutionary assumptions of the model, in line with the revision produced for regional and national projections.
The outcome is made available in three ways:
- population by sex and five-year age groups
- components of the demographic balance sheet
- main demographic indicators
Data can be downloaded directly from the internet site for all the provinces, for the provincial capital municipalities and for all municipalities, even if not capitals, which exceed 20 thousand inhabitants. Istat also makes available to users data relating to all the other Municipalities and for any kind of supra-municipal aggregation upon specific request for data to be sent to our contact center.
The municipalities considered in the study are 7,903, i.e. those existing as of 1 January 2021. The evolutionary assumptions regarding fertility, survival and migration in the various municipalities come from the regional projections, according to a top-down redistribution approach. The final summary results of the municipal projections therefore coincide with the regional ones.
Although the link between the regional and municipal forecasting model ensures not only consistency of results but also a global reference framework for the demographic evolution of all municipalities, data of this study, especially in the long term, should be used with extreme caution. The projections become, in fact, the more uncertain the further one moves away from the starting point, especially in small geographic realities such as those contemplated here. It should also be emphasized that projections represent a what-if exercise. In other words, they are elaborations in which the calculations carried out show a particular evolution of the population which is the result of the specific assumptions about the demographic behaviour. The results produced for the first forecast year also meet this principle, which in fact constitute an anticipation of the demographic balance and census data.
The final validation operations of both the demographic balance and the resident population of each Municipality, in fact, can give rise to differences between the validated data and the one initially expected to be more reliable.