Key Links in Network Interactions: Assessing Route-specific Travel Restrictions in China during the Covid-19 Pandemic

Abstract

We consider a model of network interactions where the outcome of a unit depends on the outcomes of the connected units. We determine the key network link, i.e., the network link whose removal results in the largest reduction in the aggregate outcomes, and provide a measure that quantifies the contribution of a network link to the aggregate outcomes, which complements the intercentrality measure of the key network node proposed by Ballester, Calv ́o-Armengol, and Zenou (2006). We provide an example examining the spread of Covid-19 in China. Travel restrictions were imposed to limit the spread of infectious diseases. As uniform restrictions can be inefficient and incur unnecessarily high costs, we examine the design of restrictions that target specific travel routes. Our approach may be generalized to multiple countries to guide policies during epidemics ranging from ex ante route-specific travel restrictions to ex post health measures based on travel histories, and from the initial travel restrictions to the phased reopening.

Note: Funding: Chen was supported by the US PEPPER Center Scholar Award (P30AG021342) and NIH/NIA grants (R03AG048920; K01AG053408). Qiu and Shi received support from the 111 Project of China (Grant No.B18026). Shi was supported by the National Natural Science Foundation of China (Grant No.71803062) and the Ministry of Education of China (GrantNo.18YJC790138). Conflict of Interest: None.

Keywords: network interactions, key network links, COVID-19, transmission

JEL Classification: C21, I18, D85, H75