RAPID: Exposure Indices for COVID-19 Research

We use smartphone movement data to create human exposure indices for COVID-19. The immediate outputs of the project are ready-to-use data that will enable COVID-19 research requiring information on human movement. The three indices, LEX, DEX, and VEX, study movements both within and across geographies in the United States. They measure location exposure stemming from cross-county movements, device exposure stemming from potential interactions at establishments, and venue exposure that counts visits at identified establishments, respectively. All indices are provided at a daily frequency at various granularities. In addition to these indices, we provide documentation and practical advice for using the data in research. These data can be immediately used by other researchers and policy makers in examining human exposure to COVID-19. Policy makers can utilize these resources for immediate insights on COVID-19 exposure and for modelling reopening the economy in relation to human movement.

Our analysis utilizes cell phone ping data covering millions of devices and millions of identified locations. The LEX is a matrix that utilizes smartphones pinged in a given location each day and incorporates the share of devices pinged in each location at least once during the previous two weeks. The DEX is a device-level index that incorporates the average exposure of people living in a county to other people within commercial venues. To calculate exposure, the index utilizes the number of distinct other devices the focal device interacts with through visits in a given establishment in a given day. The DEX index take into consideration that individuals sheltering in place may influence the quantity of cell phone pings for analysis. The VEX counts the number of devices that are present in the same establishment at the same time. The VEX index provides insights around establishment traffic before and after stay-at-home orders.