PATTERNS OF TRANSNATIONAL TERRORISM , 1970-99 : ALTERNATIVE TIME SERIES ESTIMATES by

Using alternative time series methods, this paper investigates the patterns of transnational terrorist incidents that involve one or more deaths. Initially, an updated analysis of these fatal events for 1970-99 is presented using a standard linear model with pre-specified interventions that represent significant policy and political impacts. Next, a (regime-switching) threshold autoregressive (TAR) model is applied to this fatality time series. TAR estimates indicate that increases above the mean are not sustainable during high-activity eras, but are sustainable during low-activity eras. The TAR model provides a better fit than previously tried methods for the fatality time series. By applying a Fourier approximation to the nonlinear estimates, we get improved results. The findings in this study and those in our earlier studies are then applied to suggest some policy implications in light of the tragic attacks on the World Trade Center and the Pentagon on 11 September 2001. PATTERNS OF TRANSNATIONAL TERRORISM, 1970-99: ALTERNATIVE TIME SERIES ESTIMATES On the morning of 11 September 2001, the world watched in horror as 19 hijackers wreaked death and destruction on the World Trade Center and the Pentagon. The lethality of transnational terrorism attained a new height, greatly out of line with the experience of the last three decades where on average 400-500 people lost their lives each year in transnational terrorist events (US Department of State, 1989-2000). In a matter of an hour, somewhere between 5000 to 6000 innocent individuals from upwards of 62 nations died in four coordinated hijackings. This attack underscores that the security threat confronting industrial nations is more from clandestine groups with perceived grievances than from rogue nations. The reliance of modern industrialized economies on technology makes them especially vulnerable to terrorist attacks, as the events of 11 September 2001 sadly demonstrate. Terrorism is the premeditated use or threat of use of extra-normal violence or brutality by subnational groups to obtain a political, religious, or ideological objective through intimidation of a huge audience, usually not directly involved with the policymaking that the terrorists seek to influence. Key ingredients of the definition include the underlying political motive, the general atmosphere of intimidation, and the targeting of those outside of the decision-making process. Terrorists choose their targets to appear to be random so that everyone feels at risk, when getting on a plane, entering a federal building, or strolling a market square. Business people, military personnel, tourists, and everyday citizens, rather than politicians, are generally the targets of terrorists attacks. In the case of the World Trade Center, the victims were not directly involved in the political decision-making process associated with the demand (i.e., the removal of the US presence from Saudi Arabia and an end to US support of Israel) that may have been behind the attacks. The incident underscores the importance of applying sophisticated analyses to the study