Does Target-hardening Result in Deadlier Terrorist Attacks against Protected Targets? An Examination of Unintended Harmful Consequences

Objectives: This study examines whether the use of target-hardening measures engenders greater amounts of casualty terrorist attacks against protected targets. Specifically, this study evaluates the impact of augmenting aviation security and protection of U.S. embassies and diplomats on the frequency and proportion of casualty attacks against aviation targets and U.S. diplomatic targets, respectively. Method: Using time-series data from the Global Terrorism Database (1970 to 2001), this study conducts time-series intervention analysis. To provide a more comprehensive test, a variety of supplementary analyses—consisting of data transformations, various onsets of the interventions, autoregressive integrated moving average, Poisson, and vector autoregression models of time-series data—are performed. Results: We found no increase in the frequency or proportion of casualty attacks against protected targets following target-hardening interventions. The results show that the typical ensuing terrorist attack against hardened targets is not violence based (i.e., maximizing casualties). Conclusions: Findings that attacks against hardened targets did not become deadlier provide support for the criminological message that unintended harmful effects from situational terrorism prevention strategies are the exception rather than the rule.