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Research Questions

  1. How valid and effective is FEMA's HSGP risk formula?
  2. How might it be improved?

The Federal Emergency Management Agency's (FEMA's) Homeland Security Grant Program (HSGP) provides a suite of grants to help strengthen U.S. communities against terrorist attacks. To inform grant resource allocation decisions, FEMA has developed and maintains a risk-based formula to assess relative threat, vulnerability, and consequences of terrorist attacks in states and major urban areas. The formula helps FEMA decide how to use finite resources for the grant programs. As a result of the evolving threat landscape and as part of ongoing efforts to improve administration of the grant program, FEMA is performing a comprehensive review of the risk formula. As part of this review, the U.S. Department of Homeland Security (DHS) asked the Homeland Security Operational Analysis Center (HSOAC) to conduct an independent review of HSGP's risk formula and data sources.

To assess the grant program's risk formula, the research team evaluated the data elements and sources in each component of the terrorism risk formula, reviewed the mathematical calculations used in the risk methodology, and considered alternative data elements and sources to account for the evolving threat environment. The evaluation framework used in this study addresses the formula's compliance with the program's authorizing language, legitimacy to stakeholders, and the validity and simplicity of the risk formula. The review suggests alternative approaches FEMA could consider to improve the risk formula and to address additional dimensions, such as community resilience and equity.

Key Findings

  • The grant risk formula is implemented effectively, consistent with program requirements, and responsive to stakeholder concerns, but the index approach used limits the formula's validity for assessing terrorism risk.
  • Shifts in the nature of the terrorism threat hamper reliable assessment of the relative likelihood of terrorist attacks against a particular jurisdiction.
  • The varied nature of today's threats suggests that terrorists’ preferred targets could become so diverse that the vulnerability component will not be able to adequately address them all.
  • Some data elements of the risk formula that are required by the program's authorizing language — originally developed in 2002 — are no longer closely associated with terrorism risk and therefore place limits on the effectiveness of the model's approach.
  • Potential modifications to address gaps would require additional research and present trade-offs for the compliance, legitimacy, validity, and simplicity of the risk formula.


  • Consider trade-offs in proposed changes to the mathematical construction of the risk formula that could simplify the formula but have uncertain effects on its legitimacy and little effect on its validity or compliance.
  • Consider clarifying which types of threat domains to include in the risk model beyond terrorism, if any, and consider complementing classified data with unclassified data to improve transparency, feasibility, and analysis of additional threat domains.
  • Consider whether existing target-based vulnerability indexes are adequate for assessing vulnerability and whether inclusion of the border index is appropriate given the nature of the threat.
  • Consider whether inclusion of the military personnel index in the consequence component is appropriate given the nature of the threat.
  • Consider conducting research to identify and evaluate equity indicators for the program and trade-offs inherent in the economic-concentration metric before adding it as a new measure.
  • Consider using alternatives to the index-based approach, such as ones based on equal distribution, experienced risk, or terrorism security capabilities.

This research was sponsored by the U.S. Department of Homeland Security (DHS) Science and Technology Directorate and conducted by the Infrastructure, Immigration, and Security Operations Program within the RAND Homeland Security Operational Analysis Center.

This report is part of the RAND research report series. RAND reports present research findings and objective analysis that address the challenges facing the public and private sectors. All RAND reports undergo rigorous peer review to ensure high standards for research quality and objectivity.

RAND is a nonprofit institution that helps improve policy and decisionmaking through research and analysis. RAND's publications do not necessarily reflect the opinions of its research clients and sponsors.