The CDC/ADSDR SVI is designed to help public health officials and local planners with preparing and responding to emergency events like hurricanes, disease outbreaks, or exposure to dangerous chemicals. The SVI databases and maps can be used to estimate the amount of supplies need (e.g. food, water, medicine, etc.), to identify areas in need of emergency shelters, to estimate the number of emergency personnel need, to create evacuation plans, and to “identify communities that will need continued support to recover following an emergency or natural disaster” (https://www.atsdr.cdc.gov/placeandhealth/svi/fact_sheet/fact_sheet.html).
The SVI determines the social vulnerability of every census tract in the United States. The index ranks each tract on 15 factors grouped into four related themes (see below).
Each census tract/county has a percentile ranking that represents the proportion of tracts/counties for which the tract/county of interest is equal to or lower in terms of social vulnerability. Higher percentile ranking values indicate greater vulnerability. For instance, ranking of 0.85 indicates that the tract/county of interest is more vulnerable than 85% of tracts/counties but less vulnerable than 15% of tracts/counties.
The CDC defines social vulnerability as the extent to which certain social conditions might affect a community’s capacity to respond to a disaster and prevent human suffering and financial loss.
Starting in 2014, the CDC has also added a database for Puerto Rice, as well as for Tribal Census Tracts, which are defined independently of standard county-based tracts.
Overall Vulnerability
1. Socioeconomic Status
- Below Poverty
- Unemployed
- Income
- No High School Diploma
2. Household Composition and Disability
- Aged 65 of Older
- Aged 17 or Younger
- Civilian with a Disability
- Single-Parent Household
3. Minority Status and Language
- Minority
- Speaks English “Less than Well”
4. Housing Type and Transportation
- Multi-Unit Structures
- Mobile Homes
- Crowding
- No Vehicle
- Group Quarters
In 2018, two adjunct variables (not included in the overall SVI rankings) were added: 2014-2018 ACS estimates for persons without health insurance, and an estimate of daytime population taken from LandScan 2018.