Heterogeneous impact of a lockdown on inter-municipality mobility

TL;DR

This study analyzes how COVID-19 lockdown measures in Portugal affected inter-municipality mobility, revealing that reductions varied based on initial mobility levels and population size, impacting virus spread pathways.

Contribution

It provides the first detailed analysis of heterogenous mobility reductions during lockdown, highlighting their implications for modeling virus transmission.

Findings

Mobility reduction ranged from 10-20% in low-mobility municipalities to over 60% in large, high-mobility areas.

Reductions depended strongly on initial outflow and population size, showing heterogeneity.

Structural changes in likely virus spread paths were identified due to mobility shifts.

Abstract

Without a vaccine, the fight against the spreading of the coronavirus has focused on maintaining physical distance. To study the impact of such measures on inter-municipality traffic, we analyze a mobile dataset with the daily flow of people in Portugal in March and April 2020. We find that the reduction in inter-municipality traffic depends strongly on its initial outflow. In municipalities where the mobility is low, the outflow reduced by $10-20\%$ and this decrease was independent of the population size. Whereas, for municipalities of high mobility, the reduction was a monotonic increasing function of the population size and it even exceeded $60\%$ for the largest municipalities. As a consequence of such heterogeneities, there were significant structural changes on the most probable paths for the spreading of the virus, which must be considered when modeling the impact of control measures.