Version 1.19 Change Summary

There have been significant data, methodology, and website changes to meet the needs of the user community and improve the quality of the National Risk Index data.

What has changed from the previous versions?

Below is a list of major enhancements:

Data and Methodology Changes

• Changed Social Vulnerability source data to the Centers for Disease Control and Prevention (CDC)/Agency for Toxic Substances and Disease Registry (ATSDR)'s Social Vulnerabilty Index (SVI).
• Updated to 2021 Census boundaries for counties, Census tracts, and Census blocks.
• Updated to 2021 Census population and building valuations for defining exposure values.
• Enhanced characterization of land use using new datasets for defining population, building, and agriculture exposure areas and values.
• Expanded results to all U.S. territories.
• Updated source datasets for the Coastal Flooding, Tsunami, and Landslide hazard types.
• Updated period of record for source datasets impacting 15 hazard types.
• Updated drought methodology to exclude impacts to livestock.
• Added new risk value and expected annual loss rate metrics.
• Changed all scores to represent national percentiles.
• Changed methods for grouping communities into rating categories.
• Updated methodology to estimated historic loss ratio values separately for urban and rural communities.
• Updated methodology to smooth historic loss ratio values for Hurricanes.

Website Changes

• Text updates to multiple pages.
• Images updated on multiple pages.
• Updated NRI datasets and metadata available for download.
• New data archive page to access previous versions of data and documentation.
• Updated the community information panel in the map to include the new expected annual loss rate metrics.
• Updated the Community Risk Profile Report to include the new expected annual loss rate and risk value metrics.
• Updated the Community Risk Comparison Report to include the new risk value metrics.

How will these changes impact the National Risk Index data?

The enhancements in this version impact all metrics for all communities. These changes leverage the best available national datasets and apply risk analysis best practices to:

• Improve the accuracy of risk metrics.
• Make the results more intuitive.
• Enable trending of risk over time.

Communities are now based on 2020 Census boundaries which differ from the previous version which was based on the 2010 Census. The use of the new CDC/ASTDR Social Vulnerability Index (SVI) improves the accuracy and clarity of the Social Vulnerability profile.

Finally, previous scores have been replaced with national percentiles to enable more intuitive comparison across communities.

Learn about the risk equation supporting the Risk Index
Understanding Scores and Ratings
For comprehensive details about the current methodology, see the National Risk Index Technical Documentation.
For comprehensive details about the changes in methodologies and data sources from each version, see the National Risk Index Data Version and Update Documentation.