A RELATIVE RISK ASSESSMENT APPROACH TO HOMELAND SECURITY

Since the events of 9/11, there have been considerable concerns and associated efforts to prevent or respond to acts of terrorism. Very often we hear calls to reduce the threat from or correct vulnerabilities to various terrorist acts. Others fall victim to anxiety over potential scenarios with the gravest of consequences involving hundreds of thousands of casualties. The problem is complicated by the fact that planners have limited, albeit in some cases significant, resources and less than perfect intelligence on potential terrorist plans. However, valuable resources must be used prudently to reduce the overall risk to the nation. A systematic approach to this process of asset allocation is to reduce the overall risk and not just an individual element of risk such as vulnerabilities. Hence, we define risk as a function of three variables: the threat (the likelihood and scenario of the terrorist act), the vulnerability (the vulnerability of potential targets to the threat), and the consequences (health and safety, economic, etc.) resulting from a successful terrorist scenario. Both the vulnerability and consequences from a postulated adversary scenario can be reasonably well estimated. However, the threat likelihood and scenarios are much more difficult to estimate. A possible path forward is to develop scenarios for each potential target in question using experts from many disciplines. This should yield a finite but large number of targetscenario pairs. The vulnerabilities and consequences for each are estimated and then ranked relative to one another. The resulting relative risk ranking will have targets near the top of the ranking for which the threat is estimated to be more likely, the vulnerability greatest, and the consequences the most grave. In the absence of perfect intelligence, this may be the best we can do.