A vulnerability index is a measure of the exposure of a population to some hazard. Typically, the index is a composite of multiple quantitative indicators that via some formula, delivers a single numerical result. Through such an index "diverse issues can be combined into a standardised framework...making comparisons possible". For instance, indicators from the physical sciences can be combined with social, medical and even psychological variables to evaluate potential complications for disaster planning.
The origin of vulnerability indexes as a policy planning tool began with the United Nations Environmental Program. One of the participants in the early task forces has also conducted secondary research documenting the evolution of the analytic tool through various stages. The term and methodology then expanded through medical literature and social work as discussed by Dr. James O'Connell of Boston Healthcare for the Homeless.
The basic methodology of constructing a vulnerability index is described by University of Malta researcher Lino Briguglio. The individual measures are weighted according to their relative importance. A cumulative score is then generated, typically by adding the weighted values. Decision trees can evaluate alternative policy options. Much of the original research has been evaluated by Lino Briguglio and presenters at Oxford, providing a body of secondary source material.
A composite vulnerability index grew out of the work of South Pacific Applied Geoscience Commission (SOPAC), Fiji, and the Expert Group on Vulnerability Indexes affiliated with the United Nations, in response to a call made in the Barbados Plan of Action, the Alliance of Small Island States (AOSIS).
Bruguglio participated in development of the vulnerability index model for international organizations of small island developing states. University of Malta also hosts the Islands and Small States Institute, Foundation for International Studies. Other institutional participants included the New Zealand Official Development Assistance (NZODA) Programme. In 1996, the concept of a composite vulnerability index had been tentatively taken up by Commonwealth policy analysts. In 1997, official background papers of the SIDS unit reflected the term "vulnerability index" at least internally. It was also advanced in Commonwealth channels. By 1997, the term was approved for publication by the staff of the UN Secretary General in the SG's Report on Development of a Vulnerability Index for SIDS. This concept was subsequently adopted by other experts in that field. and explicitly named as such.
In a 1999 Technical Report for SOPAC, Kaly et al. discussed more focused vulnerability indexes. A subsection of that report was entitled "Vulnerability index – environment" and the report also discussed the concept of "Environmental vulnerability index".
Extension of the general concept
The IPCC embraced vulnerability as a key category in 2001. A 2002 paper then applied a vulnerability indexing model to analysis of vulnerability to sea level rise for a US coastal community. At a 2008 Capacity Building Seminar at Oxford, the "Climate Vulnerability Index" was presented with an application to the protection of tourist economies, which may be important to small island states and others. By the time of this seminar, vulnerability indexes were established as governance tools. However, despite existing vulnerability assessment methodologies, vulnerability assessments are heavily influenced by data availability, data reliability, extent, scale, rating methods of vulnerability indicators, and interpretation of the 'vulnerability' and related concepts. As a result, there are many frameworks and indices available which are attuned to specific systems, areas, or circumstances, rather than a comprehensive definition or framework.
In hazard planning
The concept has been extended and applied in dealing with risk from natural hazards and the part that population metrics play in making such a situation into a disaster. In the USA this has been done at a county level. And is run by the Hazards and Vulnerability Research Institute  since 2003.
In 2005 a "Histopathological Plaque Vulnerability Index" was proposed. Thereafter, the term was adopted by Dr Jim O'Connell, at Boston's Healthcare for the Homeless. The model was also adopted by Common Ground, an advocacy organization in New York City which promulgated the vulnerability index to Santa Monica, New Orleans, Washington, DC, and what their literature referred to as "Los Angeles County's infamous Skid Row". It utilizes eight key health indicators that measure a chronically homeless person's vulnerability to early death. The model is now being adopted and registry week drives in the "inner city areas" of Brisbane, Melbourne and Sydney.
- Disaster planning
- Emergency medicine
- Host factor
- Infectious disease
- Mortality rate
- Standardized mortality ratio
- The Climate Vulnerability Index:relevance to the Tourism Sector
- List of Vulnerability Studies
- Homelessness and the Vulnerability Index: A Guide to Registry Week Results in the Omaha Metro Region
- Juneau Economic Development Council (2009). "Vulnerability Index: Prioritizing the Street Homeless Population by Mortality Risk" (PDF). Common Ground. Retrieved 25 May 2013.
- O'Connor, James| Unpublished public forum presentation|University of Santa Barbara|Santa Barbara, California 2011
- Briguglio, Lino (1992). "Preliminary Study on the Construction of an Index for Ranking Countries According to their Economic Vulnerability". UNCTAD/LDC/Misc.4.
- Pantin, D. (1997). Alternative Ecological Vulnerability Indicators for Developing Countries with Special Reference to SIDS. Report prepared for the Expert Group on Vulnerability Index. UN(DESA), 17–19 December 1997.
- SOPOAC Technical Report 275
- Briguglio, L. (1992). Preliminary Study on the Construction of an Index for Ranking Countries According to their Economic Vulnerability, UNCTAD/LDC/Misc.4 (1992).
- Wells, J. (1996). Composite Vulnerability Index: A Preliminary Report. London: Commonwealth Secretariat.
- United Nations – DPCSD (1997). Vulnerability Index (Revised Background Paper). SD-SIDS Unit.
- Wells, J. (1997). Composite Vulnerability Index: A Revised Report. London: Commonwealth Secretariat.
- United Nations (1997). Report of the Secretary-General on the Development of a Vulnerability Index for Small Island Developing States (Advance Unedited Version to be submitted to the Commission for Sustainable Development, Sixth Session, 20 April-1 May 1998, and to the Committee for Development Planning, 32nd session, 4–8 May 1998).
- Easter, C. (1998). 'Small States and Development: A Composite Index of Vulnerability' in Small States: Economic Review and Basic Statistics, Commonwealth Secretariat, December 1998
- Crowards, T. (1999). An Economic Vulnerability Index for Developing Countries, with Special Reference to the Caribbean: Alternative Methodologies and Provisional Results. Caribbean Development Bank, March 1999.
- IMPACTS, ADAPTATION, AND VULNERABILITY/Climate Change 2001: Impacts, Adaptation, and Vulnerability is the most comprehensive and up-to-date scientific assessment of the consequences of, and adaptation responses to, climate change.
- Vulnerability of coastal communities to sea-level rise: a case study of Cape May County, New Jersey, USA
-  Wolters, M., Kuenzer, C., 2015: Vulnerability Assessments of Coastal River Deltas – Categorization and Review. Journal of Coastal Conservation, Planning and Management- DOI 10.1007/s11852-015-0396-6
- Tang, Dalin; et al. (December 2005). "Local Maximal Stress Hypothesis and Computational Plaque Vulnerability Index for Atherosclerotic Plaque Assessment". Ann Biomed Eng. 33 (12): 1789–801. doi:10.1007/s10439-005-8267-1. PMC 1474005. PMID 16389527.
- Other Common Ground Initiatives