Vulnerability Assessment

Social Vulnerability Index (SVI) - An Overview

PRESENTER: Welcome to our video, Introduction to CDC's Social Vulnerability Index, also known as the SVI. Please visit svi.cdc.gov to explore our website and interactive maps after this presentation.

All communities exhibit varying degrees of physical vulnerability to potential disaster, both natural and human caused. However, it is a community's social vulnerability that may determine how well it responds to and recovers from a disaster.

Studies have shown the socially vulnerable are often less prepared for a disaster event, less likely to recover from it, and more likely to be injured or die. Effectively addressing social vulnerability decreases human suffering and reduces post-disaster cost to society.

Our group at ATSDR, known as GRASP, developed the SVI to help identify socially vulnerable populations before, during, and after hazardous events.

The SVI is a database that ranks the relative social vulnerability of US census tracts. We score and rank each tract in the nation on each of 15 census variables to determine its social vulnerability. The right side column of this graphic shows the variables we use in the SVI. The 15 census variables are further grouped into four themes. Tracts are ranked on these four themes, as well.

Finally, the sums of the scores for the 15 individual variables are ranked for each tract to determine overall vulnerability. So there are three ranking options for each tract, for each variable, for each theme, and overall.

Our rankings were calculated using a percentile ranking method. A percentile rank of 0 means least vulnerable. A percentile rank of 1 means most vulnerable. All census tracts are ranked between 0 and 1. As an additional measure, we flag tracts with any variables ranked at 0.9 or more, to help us easily identify tracts that are particularly vulnerable. We also determined tract rankings within individual states.

Here are SVI maps of Gwinnett County, Georgia, showing each of the four themes, as well as its overall social vulnerability. As you can see, the vulnerability of any given tract may vary by theme. Some tracts are highly vulnerable for all four themes, and will likely have the highest vulnerability overall. Other tracts may be highly vulnerable on one or more themes, or have low vulnerability on all themes.

You can use the interactive mapping application to create a map showing the social vulnerability of your own community, county, or state. And you can examine the detailed social vulnerability and ranking of any tract in the United States, as well as download SVI data and tools. Other data, including such features as hospitals or schools, can be combined with information on impending hazards to assess overall risk to a community. Emergency planners can direct specific attention to areas most in need of funding and physical support over the course of a disaster event.

There are many potential uses for the SVI. Please visit the SVI website at svi.cdc.gov. Learn more about our methods and how to use the interactive map in our other videos. Thank you.