Social Vulnerability Index for the United States - 32 Variables
The Social Vulnerability Index (SoVI®) 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
The index synthesizes 32 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 were culled from
national data sources, primarily those from the United States Census Bureau.
The data were compiled and processed by the Hazards and Vulnerability Research Institute at the
University of South Carolina. The data were standardized and placed into a principal components
analysis to reduce the initial set of variables into a smaller set of statistically optimized
components. Adjustments were made to the components’ cardinality (positive (+), negative (-),
or absolute value (ll)) to insure that positive component loadings were associated with increasing
vulnerability, and negative component loadings with decreasing vulnerability. Once the cardinalities
of the components were determined, the components were added together to determine the numerical
social vulnerability score for each county. For SoVI® 2000, there are 9 significant components
explaining 76% of the variance in the data. Among them are socioeconomic status, elderly and children,
rural agriculture, housing density,
black female-headed households, gender, service
industry employment, unemployed Native Americans, and infrastructure employment.
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).
Instructions on how to calculate this version of SoVI® can be
Maps using this data can be found here.