Centers for Disease Control and Prevention (CDC) Social Vulnerability Index (SVI)

Description:

Social Vulnerability encompasses demographic and socioeconomic factors—such as poverty, limited access to transportation, and crowded housing—that make certain communities more susceptible to hazards and stressors. These stressors may include natural or human-made disasters, like tornadoes or chemical spills, as well as disease outbreaks, such as COVID-19.

The CDC/ATSDR Social Vulnerability Index (SVI), managed by the Geospatial Research, Analysis & Services Program (GRASP), is a place-based index, database, and mapping tool designed to identify and quantify socially vulnerable communities. This index helps public health officials and local planners better prepare for and respond to emergencies, aiming to reduce human suffering, economic loss, and health inequities. Over time, the CDC/ATSDR SVI has evolved, and it strongly discourages comparisons across different versions of the database. Each database calculates percentile scores by ranking census tracts relative to others within the same year, so scores from different years are not directly comparable. Adjustments to the SVI categories have been made periodically to reflect updates in U.S. Census Bureau data and incorporate the latest research.

The current SVI uses 16 U.S. Census variables from the 5-year American Community Survey (ACS) to identify communities that may need support during or after disasters. These variables are grouped into four themes representing major areas of social vulnerability, which are then combined into a single measure. The GRASP program assigned each geography a percentile ranking for each variable and calculated an overall score for each category by summing these percentiles. Each of the four themes is then assigned a percentile ranking, which contributes to the overall Social Vulnerability Index. Based on the overall SVI score, communities are classified into four vulnerability levels: Low, Low to Moderate, Moderate to High, and High, dividing all tracts or counties into quantiles. A percentile ranking represents the proportion of tracts (or counties) with equal or lower vulnerability than a given tract or county. For example, a ranking of 0.85 signifies that 85% of tracts (or counties) in the state or nation are less vulnerable, while 15% are more vulnerable. Find more information on the CDC’s Social Vulnerability Index at https://svi.cdc.gov/.