Temporary Displacement from Metropolitan Areas in Italy during COVID-19

Mobility data have been recognized as a vital source of information to face the recent pandemic of a novel coronavirus (COVID-19). Indeed, they can provide actionable insights to understand the im- pact of political decisions, by providing near real-time evidence of changes in human connectivity. In this paper we provide a practical use case on the repercussions of restrictive policies on the Italian mobility. To this aim we leverage a massive dataset of human movements based on "Disease Prevention Maps", made available by Facebook to the research community through its "Data for Good" initiative. We build a network representation of the evolution of mobility during the lockdown, and highlight a reduction of connections between different administrative units at all geographical levels (municipalities, provinces and regions), with a consequent increase of inner mobility within municipalities. Finally, we highlight an interesting trend of depopulation of metropolitan areas, as large cities experience a sharp shrinkage in the number of citizens while small towns are characterized by a growth of residents, and provide hypotheses on key determinants of this phenomenon.