Assessing the degree of territorial embeddedness among population subgroups: a first proposal

In studies examining the settlement patterns of foreign communities within a region, the primary aim often involves assessing the level of spatial segregation compared to the native population. However, such analyses typically overlook the assessment of the historical presence of these communities in the region. Particularly with small-sized communities, their long-standing presence in the region becomes a significant factor in characterizing both the community and the region itself. This permanence can be seen as a form of embeddedness. It's important to note that the duration of a subgroup's presence in the population may not align with the individual members' length of stay. In some cases, while individual members may have short stays, the community as a whole may maintain a consistent presence over time due to ongoing turnover. To address this aspect, we propose an index that measures the permanence of a population subgroup within a region over a specified time interval, relying solely on its total balance, observed during that period. This index could serve as a straightforward measure of population stability or rootedness, capturing only the overall gains or losses (in terms of time) within the subgroup rather than focusing on the separate contribution of births, deaths, immigration, and emigration. This index is complemented by the evaluation of its uncertainty, by assuming the goodness of the indicator is based on the stationarity of the historical series of values computed on the sub-periods. To support the utility of this index, we apply it to population subgroups categorized by citizenship in the Metropolitan Area of Milan.