CDC SVI Documentation 2000
View print only version of CDC SVI 2000 Documentation pdf icon[PDF – 122 KB]
About the Data
The interactive maps are visual representations of the Social Vulnerability Index (SVI), which data were extracted from US Census 2000 for the fifty states and District of Columbia at census tract level. The SVI was constructed using the following procedure:
- Percentile Ranking. Each of fifteen Census and ACS variables* was ranked from highest to lowest across all census tracts in the US with a non-zero population.**
- A percentile rank is defined as the proportion of scores in a distribution that a specific score is greater-than or equal-to. Percentile ranks were calculated using the formula:
Percentile Rank = (Rank-1)/ (N-1)
Where N = the total number of data points and all sequences of ties are assigned the smallest of the corresponding ranks.
Rankings range from 0.00 to 1.00 with 0.00 being those tracts least vulnerable for a particular variable and 1.00 being those tracts most vulnerable for a particular variable.
- The fifteen variables for each tract were also grouped into four thematic domains (socioeconomic, household composition/disability, minority status/language, housing/transportation) – and four domain rankings were calculated for each tract.
- An overall social vulnerability ranking was calculated from the four domain rankings. The overall Social Vulnerability ranking of census tracts is displayed on the maps as TOTAL PERCENTILE.
- We also created within-state rankings for the individual states in the U.S. When the user selects a state or county map, the underlying ranked data drives the display of the map.
- Tracts having census variables ranking in the top 10 percent of all values, i.e., at the 90th percentile, were also flagged for high vulnerability. The effort here is to identify vulnerable tracts whose overall vulnerability ranking masks high vulnerability scores on individual variables.
- The user may also separately display each of the four domains at either national- or state-level.
- Zip-code areas and FEMA/Census Regions may also be displayed, but do not generate data or percentile rankings as such.
For more information on the method used to construct the SVI, please click here to see: “A Social Vulnerability Index for Disaster Management pdf icon[PDF – 2 MB] ”
*The fifteen U.S. Census variables are: percent individuals below poverty, percent civilian unemployed, per capita income, percent persons aged 25 and older with no high school diploma, percent aged 65 and older, percent aged 17 and under, percent persons older than 5 years with a disability, percent single-parent households with children under 18 years of age, percent minority, percent persons 5 years and older who speak English less than well, percent housing structures with 10 or more units, percent mobile homes, percent households with more than one person per room, percent households with no vehicle available, and percent persons in group-quarters.
**Per capita income was ranked from lowest to highest because, unlike other variables, a higher value indicates lesser vulnerability.
SVI 2000 Data Dictionary
For information on how the SVI was constructed, please see A Social Vulnerability Index for Disaster Management. pdf icon[PDF – 2 MB]
|2. Household Composition/Disability|
|3. Minority Status/Language|
|4. Housing Type/Transportation|