Dynamic Social Vulnerability Index (DSVI): A Mobility-Adjusted Measure of Community Vulnerability

The Centers for Disease Control and Prevention and Agency for Toxic Substances and Disease Registry Social Vulnerability Index (SVI) serves as a useful tool to identify vulnerable communities in order to meet their needs before, during, and after disasters, infectious disease outbreaks, and other public health emergencies. Additionally, the SVI is widely used in social science research as a proxy measure of social disparities and as a measure of a community’s social determinants of health. We argue that social vulnerability, assessed in terms of a community’s access to different resources, is not solely determined by residential location but also by the locations that its residents frequent throughout the day, as determined by their movement. Building on the concept of activity spaces for individuals, we propose the idea of an ``activity space for communities'', which is an aggregate measure of the activity space of all individuals who consider that community their ``home''. In aggregate, residents of different communities will tend to have very different movement patterns, and hence different activity spaces. Using large-scale cell-phone telemetry data for the United States in 2019, we quantify this activity space for communities at the census tract level and apply it to SVI to develop a mobility adjusted measure of community vulnerability - the Dynamic SVI (DSVI). By incorporating mobility patterns into SVI, we move toward a relational and dynamic model of vulnerability, where risk is understood not just as a product of fixed geographic location, but also as shaped by daily movements, access to transportation, and the spatial distribution of critical resources and services. A web application to explore and download the DSVI for 2019 is available at https://mobility.science/dsvi.