Evaluating the impact of demographic, socioeconomic factors, and risk aversion on mobility during COVID-19 epidemic in France under lockdown: a population-based study

On March 17, 2020, French authorities implemented a nationwide lockdown to respond to COVID-19 epidemic and curb the surge of patients requiring critical care, similarly to other countries. Evaluating the impact of lockdown on population mobility is essential to quantify achievable reductions and identify the factors driving the changes in social dynamics that affected viral diffusion. We used temporally resolved travel flows among 1,436 administrative areas of mainland France reconstructed from mobile phone trajectories. We measured mobility changes before and during lockdown at both local and country scales. Lockdown caused a 65% reduction in countrywide number of displacements, and was particularly effective in reducing work-related short-range mobility, especially during rush hours, and recreational trips. Geographical heterogeneities showed anomalous increases in long-range movements even before lockdown announcement that were tightly localized in space. During lockdown, mobility drops were unevenly distributed across regions. They were strongly associated with active population, workers employed in sectors highly impacted by lockdown, and number of hospitalizations per region, and moderately associated with socio-economic level of the region. Major cities largely shrank their pattern of connectivity, reducing it mainly to short-range commuting. Lockdown was effective in reducing population mobility across scales. Caution should be taken in the timing of policy announcements and implementation, as anomalous mobility followed policy announcements that may act as seeding events. On the other hand, risk aversion may be beneficial in further decreasing mobility in largely affected regions. Socio-economic and demographic constraints to the efficacy of restrictions were also identified. The unveiled links between geography, demography, and timing of the response to mobility restrictions may help design interventions that minimize invasiveness while contributing to the current epidemic response.ANR projects EVALCOVID-19 (ANR-20-COVI-0007) and DATAREDUX (ANR-19-CE46-0008-03); EU H2020 grants RECOVER (H2020-101003589) and MOOD (H2020-874850); REACTing COVID-19 modeling grant.