Public Security Enhances the Effectiveness of Private Security in Reducing Maritime Piracy Harm

Private security outnumbers public security, yet little is known about how private security complements public security to mitigate the severity of damage caused by criminal actors. A noteworthy context in which private and public security interact is on the high seas where vessels face danger from maritime pirates. This paper quantifies the relationship between public security in aiding private security to enhance the safety of passing vessels, as measured by the likelihood of boarding and hijacking respectively. We hypothesize that on-board private security reduces boarding and hijackings, while public security can deter hijacking of anchored vessels. Our empirical estimates find that public security amplifies the effect of private security, increasing its effectiveness by an additional 29 percentage points (pp) in aggregate. However, there is meaningful heterogeneity in the quality and size of the moderating effects of public security. Low-intensity public security, measured by a country’s military expenditures or patrol boats, only amplifies private security’s effectiveness against boarding by 21–23 pp, while high-intensity public security amplifies private security’s effectiveness by 56–77 pp. Thus, the likelihood that a vessel with private security and high-intensity public security is boarded is nearly zero. There are no significant differences in hijacking, which is a relatively rare event. A likely interpretation is that private and high-intensity public security have complementary skills, such as public security offering air support and private security offering a more permanent and responsive presence.