JUE Insight: Urban flight seeded the COVID-19 pandemic across the United States
研究发现美国疫情期间出现大规模城市外逃，迁入地区随后新增病例更多，且外逃人群更年轻、更白、更富裕，迁移与病例增长的关系在社会网络工具变量下依然成立。
We document large-scale urban flight in the United States during the COVID-19 pandemic. Regions that saw migrant influx experienced greater subsequent new COVID-19 cases, linking urban flight (as a disease vector) and coronavirus spread in destination areas. Urban residents fled to socially connected areas, consistent with the theory that individuals sheltered with friends and family, or in second homes. Populations that fled were disproportionately younger, whiter, and wealthier. The association between migration and subsequent new cases persists when instrumenting for migration with social networks.