Social Vulnerability Index for the United States

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 disasters.

The index synthesizes 42 socioeconomic and built environment 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 socioeconomic and built environment data were compiled and geo-referenced by the Hazards Research Lab at the University of South Carolina. The socioeconomic and built environment variables were standardized and input into a principal components analysis to reduce the number of variables into a smaller set of indicators. Adjustments were made to the component’s directionality (negative, positive) to insure that positive loadings were associated with increasing vulnerability, and negative loadings with decreasing vulnerability. Once the directions of the loadings were determined, the components were added together to determine the numerical social vulnerability score for each county. For SoVI 2000, there are 11 significant components and these explain 78% of the variance in the data. Among them are socioeconomic status, elderly and children, development density, rural agriculture, race, gender, ethnicity, infrastructure employment, and county debt/revenue.

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).

The initial SoVI methodology and results for 1990 were originally published in:
S. L. Cutter, B. J. Boruff, and W. L. Shirley 2003. “Social Vulnerability to Environmental Hazards,” Social Science Quarterly 84 (2): 242-261.

Instructions on how to calculate SoVI can be found here.

The database was supported by grants from the National Science Foundation
(CMS#99053252 and CMS#0220712).
www.sovius.org