[论文解读] Urban Exodus? Understanding Human Mobility in Britain During the COVID-19 Pandemic Using Facebook Data

Francisco Rowe, Alessia Calafiore+3 more|arXiv (Cornell University)|Jun 1, 2022

COVID-19 epidemiological studies被引用 5

一句话总结

使用来自2100万用户的匿名Facebook出行数据，本研究分析了2020年3月至2021年8月期间英国城乡之间的人口流动模式。研究发现，在严格封锁期间出行量出现暂时性下降，从高密度地区向低密度地区出行增加——这支持了关于‘城市撤离’的传闻——但表明这些变化是短暂的，随着限制措施解除，出行量已恢复至疫情前水平，表明全国出行模式未发生持久结构性变化。

ABSTRACT

Existing empirical work has focused on assessing the effectiveness of non-pharmaceutical interventions on human mobility to contain the spread of COVID-19. Less is known about the ways in which the COVID-19 pandemic has reshaped the spatial patterns of population movement within countries. Anecdotal evidence of an urban exodus from large cities to rural areas emerged during early phases of the pandemic across western societies. Yet, these claims have not been empirically assessed. Traditional data sources, such as censuses offer coarse temporal frequency to analyse population movement over short-time intervals. Drawing on a data set of 21 million observations from Facebook users, we aim to analyse the extent and evolution of changes in the spatial patterns of population movement across the rural-urban continuum in Britain over an 18-month period from March, 2020 to August, 2021. Our findings show an overall and sustained decline in population movement during periods of high stringency measures, with the most densely populated areas reporting the largest reductions. During these periods, we also find evidence of higher-than-average mobility from highly dense population areas to low densely populated areas, lending some support to claims of large-scale population movements from large cities. Yet, we show that these trends were temporary. Overall mobility levels trended back to pre-coronavirus levels after the easing of non-pharmaceutical interventions. Following these interventions, we also found a reduction in movement to low density areas and a rise in mobility to high density agglomerations. Overall, these findings reveal that while COVID-19 generated shock waves leading to temporary changes in the patterns of population movement in Britain, the resulting vibrations have not significantly reshaped the prevalent structures in the national pattern of population movement.

研究动机与目标

• 通过实证方法评估英国早期新冠疫情期间大城市向农村地区迁移的‘城市撤离’说法。
• 研究非药物干预措施如何重塑城乡连续体中的空间出行模式。
• 通过使用Facebook提供的高频出行数据，克服传统数据源（如人口普查）的局限性。
• 确定疫情是否导致英国全国范围内人口流动模式的永久结构性转变。

提出的方法

• 利用覆盖2100万次观测的英国各地Facebook用户匿名聚合出行数据。
• 追踪不同地方当局之间的每日出行模式，以评估城乡间出行变化。
• 通过基于密度的地方当局分类，绘制城乡连续体中的出行流动图。
• 将出行趋势与政府实施的严格程度措施相关联，以评估封锁措施的影响。
• 应用时间序列分析，比较疫情限制措施实施前后各阶段的出行水平。
• 采用对照组方法，将政策干预导致的出行变化与更广泛的行为变化分离开来。

实验结果

研究问题

• RQ1 英国在新冠疫情期间初期是否经历了从城市向农村的大规模人口迁移？
• RQ2 非药物干预措施的实施如何影响不同人口密度区域的出行模式？
• RQ3 封锁期间观察到的出行模式变化是暂时的，还是预示着人口流动的长期转变？
• RQ4 在严格程度较高的时期，前往低密度农村地区的人数是否显著增加，如传闻所述？
• RQ5 限制措施解除后，出行模式在多大程度上恢复至疫情前水平？

主要发现

• 在严格程度较高的时期，英国整体人口出行量显著下降，其中高度城市化地区降幅最为明显。
• 在封锁期间，从高密度地区向低密度地区出行出现临时性增加，为‘城市撤离’叙事提供了部分实证支持。
• 观察到的农村地区出行增加是短暂的，随着限制措施解除而逆转，出行量已恢复至疫情前水平。
• 在干预措施放宽后，前往高密度城市集聚区的出行量增加，而前往低密度农村地区出行量则减少。
• 疫情并未导致全国范围内城乡连续体中人口流动模式的永久结构性转变。
• 本研究结论认为，尽管疫情造成了出行的临时中断，但英国人口流动的潜在空间结构基本保持不变。