Inspecting ship containers for nuclear weapons is a daunting task. More than 11.6 million cargo containers enter U.S. ports each year, with 32,000 maritime containers entering ports each day. Ninety percent of containers enter through 10 of the highest-volume ports, but there are more than 300 ports operating in the United States.
The United States currently inspects about five percent of containers entering the country. With funding from the University of Southern California-based Center for Risk and Economic Analysis of Terrorism Events, Industrial and Systems Engineering and Engineering Physics Professor Vicki Bier conducted a decision analysis on the potential impact that 100-percent inspection and the threat of retaliation would have on deterring smuggling of nuclear weapons in container freight, as well as whether partial inspection might also have a deterrent effect. “We attempted to quantify the model as best we could. It involves complex considerations. How confident can we be that there would be retaliation? How confident can we be that the smuggler believes there would be retaliation? What if the attacker has multiple weapons?” Bier says. “The analysis tells you under what conditions you could achieve deterrence. It is based on an assumption that the smugglers are operating rationally, which they may or may not be.”
Based on publicly available data, Bier’s team quantified a game-theoretic model of terrorist decision making to understand the subject. The results suggest that unless the defender imposes high retaliation costs on the attacker, 100-percent inspection is likely to be needed, and deterrence with partial inspection may not be achievable in practice even though it is possible in theory. On the other hand, when the defender can credibly threaten the attacker with costly retaliation, partial inspection may be sufficient to deter nuclear smuggling attempts. Thus, for policy debates about how to prevent nuclear terrorism, consideration of the diplomatic stance on retaliation is as important as, or maybe even more important than, debate about the optimal percentage of containers to inspect.