Social Vulnerability Index for the United States - 2005-09
The Social Vulnerability Index (SoVI®) 2005-09 measures the social vulnerability
of U.S. counties to environmental hazards. The index is a comparative metric that
facilitates the examination of the differences in social vulnerability among counties. SoVI® is a valuable tool for policy makers and practitioners. It graphically illustrates the geographic variation in social vulnerability. It shows where there is uneven capacity for preparedness and response and where resources might be used most effectively to reduce the pre-existing vulnerability. SoVI® also is useful as an indicator in determining the differential recovery from disasters.
The index synthesizes 31 socioeconomic variables, which the research literature suggests
contribute to reduction in a community’s ability to prepare for, respond to, and recover
from hazards. The data are culled from national data sources, primarily those from the
United States Census Bureau.
The data are compiled and processed by the Hazards and Vulnerability Research
Institute at the University of South Carolina. The data are standardized and placed
into a principal components analysis to reduce the initial set of variables into a
smaller set of statistically optimized components. Adjustments are made to the
components’ cardinality (positive (+) or negative (-)) to insure that positive
component loadings are associated with increased vulnerability, and negative
component loadings are associated with decreased vulnerability. Once the
cardinalities of the components are determined, the components are added
together to determine the numerical social vulnerability score for each county.
SoVI® 2005-09 marks a change in the formulation of the SoVI® metric from earlier
versions. New directions in the theory and practice of vulnerability science
emphasize the constraints of family structure, language barriers, vehicle
availability, medical disabilities, and healthcare access in the preparation for
and response to disasters, thus necessitating the inclusion of such factors in SoVI®.
Extensive prior testing of SoVI®, along with the introduction of the U.S. Census Bureau’s
five-year American Community Survey estimates, permits changes to the SoVI® recipe,
resulting in an overall more robust metric.
In SoVI® 2005-09, seven significant components explain 69% of the variance
in the data. These components include
race and class;
care dependent females;
Native American ethnicity;
and service industry employment. Detailed information on these components can be found here in PDF format.
To visually compare the SoVI® scores at a national level, they are mapped
using quantiles. Scores in the top 20% of the United States are more vulnerable
counties (red) and scores in the bottom 20% of the United States indicate the least
vulnerable counties (blue).
For more details on the evolution of SoVI®, please look here.
A dicussion regarding our error correction method for the data can be found here.
Information on previous SoVI® formulations using the 2000 Census can be found using the menu above.