Finally, the team analyzed and factored in historical data from the Terrorism Knowledge Base and the Global Terrorism Data Base. The research yielded over 1,000 unique terrorist-related incidents in the targeted cities, spanning a 30 year period.

The study, sponsored by the Department of Homeland Security, yielded some unanticipated results. For instance, Boise, Idaho was ranked 10th, primarily due to its position near a major dam and vulnerability for major forest fires. City officials acknowledged surprise at the rating, and initiated contact with both Piegorsch and the state’s Homeland Security officials for clarification on the study and its results.

The overall results show that the eastern and southern seaboards of the U.S. are at greatest risk, and also indicate a large swath of vulnerability from Texas to Ohio. The cities that scored highest overall were New Orleans, LA followed by Baton Rouge, LA; Charleston, SC; Norfolk, VA; the New York/Newark area; and Washington, D.C.

As with all studies, particularly those engaged in predictive analysis, some factors had greater weight than others. For instance, Piegorsch readily admits that "Nuclear power plants and military facilities did not come up as high risk in our analysis". Although this assessment runs contrary to many other studies and theories on potential terrorist targets, the study’s results are certainly worthy of further review and analysis. A follow on study could assess whether federal funding is going to the right cities for the right programs, to maximize resource allocation. Local authorities in the cities identified might use the results as a springboard to initiate specialized training, or augment their Critical Infrastructure Protection program. Business owners may want to reassess their insurance coverage; many large firms now offer specialized policies, such as AIG which recommends Property Terrorism Insurance to cover owners in the event of loss or damage due to terrorist attacks.

In the concluding paragraph of the study, the author states that the bottom line is that “place matters”. But Piegorsch wants the public to remember that the report doesn't try to predict where terrorists might attack. "It's not probability of being a target," he said. "It's vulnerability."

Jenni Hesterman is a retired Air Force colonel and counterterrorism specialist. She is a senior analyst for The MASY Group, a Global Intelligence and Risk Management firm that supports both the U.S. Government and leading corporations. She is also an adjunct professor at American Military University, teaching courses in homeland security and intelligence studies.