SUMMARY
After the September 11, 2001 terrorist attacks, officials at all levels of government were faced with difficult policy decisions concerning public security. Many policymakers were asked to make security decisions based on limited information about the nature or credibility of potential threats. Using San Francisco as a case study, this article applies the technique of cost-benefit analysis from "yellow to orange." The article demonstrates how a policymaker might conduct a cost-benefit analysis when the benefits and costs of a decision are contingent on the unknown probability of an event occurring. This analysis highlights the importance of information sharing between levels of government and demonstrates the affect of a policy decision on the probability of terrorist attack. The lessons learned provide important insights for the many government officials currently facing risk-dependent policy decisions.