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Abstract
Compared to most types of criminal violence, terrorism poses special data collection challenges. In response, there has been growing interest in open source terrorist event data bases. One of the major problems with these data bases in the past is that they have been limited to international events—those involving a national or group of nationals from one country attacking targets physically located in another country. Past research shows that domestic incidents greatly outnumber international incidents. In this paper we describe a previously unavailable open source data base that includes some 70,000 domestic and international incidents since 1970. We began the Global Terrorism Database (GTD) by computerizing data originally collected by the Pinkerton Global Intelligence Service (PGIS). Following computerization, our research team has been working for the past two years to validate and extend the data to real time. In this paper, we describe our data collection efforts, the strengths and weaknesses of open source data in general and the GTD in particular, and provide descriptive statistics on the contents of this new resource.
Support for this work was provided by the National Institute of Justice (NIJ), grant number 2002-DT-CX-0001, the National Center for the Study of Terrorism and Responses to Terrorism (START)—a Department of Homeland Security (DHS) Center of Excellence, and the Human Factors Division of DHS. Any opinions, findings, and conclusions or recommendations in this document are those of the authors and do not necessarily reflect the views of NIJ or DHS. We want to especially thank Hugh Barber, who helped us greatly in interpreting the original PGIS data. We also want to thank Gary Ackerman, Charles Blair, and an anonymous reviewer for their helpful comments on an earlier draft and the many students who have worked to computerize and validate these data, especially Heather Fogg, who supervised the undergraduate data collection, and Robert Apel, Bradley Bartholomew, Rhonda S. Diggs, Susan Fahey, Derrick Franke, Kevin Franke, Nadine Frederique, Rachelle Giguere, James Hendrickson, Haris Khan, Raven Korte, Lauren Metelsky, Erin Miller, Nancy Morris, Jeff Scott and Mischelle van Brakle.
Notes
Gary LaFree and Laura Dugan, “How Does Studying Terrorism Compare to Studying Crime?,” in M. DeFlem, ed., Terrorism and Counter-Terrorism: Criminological Perspectives (New York: Elsevier, 2004), 53–74.
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The organizations and individuals collecting open source terrorism data continues to evolve. For another recent effort, see William Hale, “Information versus Intelligence: Construction and Analysis of an Open Source Relational Database of Worldwide Extremist Activity,” International Journal of Emergency Management 3 (2006): 280–297.
The actual recording of a source was one of the data collection strategies that evolved over time for the PGIS data collectors. Thus, in 1970 the original PGIS data only included a source in 32 percent of the recorded terrorist incidents. By 1978, PGIS data collectors recorded specific sources for the events recorded in 95 percent of the cases. By the early 1980s, nearly all incidents had at least one source recorded.
E. F. Mickolus, International Terrorism: Attributes of Terrorist Events, 1968–1977 (ITERATE 2) (Ann Arbor, MI: Inter-University Consortium for Political and Social Research, 1982).
Walter Enders and Todd Sandler, The Political Economy of Terrorism (Cambridge, UK: Cambridge University Press, 2006).
Dennis Pluchinsky, “The Evolution of the U.S. Government's Annual Report on Terrorism: A Personal Commentary,” Studies in Conflict and Terrorism 29 (2006): 91–98.
Gary LaFree and Laura Dugan, “Building and Analyzing a Comprehensive Open Source Data Base on Global Terrorist Events, 1968 to 2005,” grant proposal to National Institute of Justice (2004).
Bruce Hoffman, Recent Trends and Future Prospects of Terrorism in the United States (Santa Monica, CA: RAND, 1998), 38.
Gary LaFree and Laura Dugan, “The Impact of Economic, Political, and Social Variables on the Incidence of World Terrorism, 1970 to 1997,” grant proposal to the National Institute of Justice (2002), 1–41.
It was not possible to directly and systematically compare the PGIS data with RAND and ITERATE given the differences in the definitions and scope of terrorism attacks between PGIS data and the other datasets. However, we were able to use RAND and ITERATE data to update and append cases when appropriate. We regard updating the data as an ongoing task that will continue after the data are released as new or more valid information continues to surface.
The current committee includes Gary Ackerman, Victor Asal, Martha Crenshaw, Laura Dugan, Michelle Keeney, Gary LaFree, Clark McCauley, and Alex P. Schmid.
All open source terrorism data bases struggle with this problem. For example, the State Department Patterns data included what the authors considered to be “significant” terrorist events, but what constituted significant property damage was left undefined until the NCTC took over the data base in 2004—henceforth significant property damage was defined as $10,000 or more.
It is the act taken as a totality that is considered, irrespective of whether every individual involved in carrying out the act was aware of it. As long as the act is the result of someone's conscious decision, it meets the criterion. Because determining intentionality is difficult, this criterion is assumed to be met based on prima facie evidence unless there is some indication otherwise. Also, whether or not the actual target was the intended target, so long as there was an intention to use violence, this criterion is met. For example, mistaken identity assassinations satisfy this criterion.
When a state finances, arms, trains, or otherwise influences a non-state group, but does not directly control its behavior and the members of the terrorist group are not employees of the state, then the group can still be regarded as a terrorist group and its actions be considered terrorist actions. If, however, a state plays an active (and determinative) role in the planning of attacks or other activities of the terrorist group (i.e., substantially controls the group's actions), then we do not consider the group to be a separate, non-state entity, but rather we regard it as part of a state's covert apparatus to be used against other states or groups. In this case, the activities of the group are not included in the data base.
Although incidents with purely economic motives are not included in the GTD itself, the collection process still records those incidents in which a known terrorist group (e.g., PKK or FARC) conducts an action for fundraising purposes.
We should also note that it is the act taken as a totality that is considered, irrespective of whether every individual involved in carrying out the act was aware of this intention. Thus, as long as a planner or decision maker behind the attack intended to coerce or publicize an issue, the intentionality criterion is met.
Note that any action satisfying two of these three criteria qualifies, irrespective of the nature of the actor or the motive, as long as the actor or motive is not specifically excluded from the list.
R. Falkenrath, “Analytic Models and Policy Prescription: Understanding Recent Innovation in U.S. Counterterrorism,” Journal of Conflict and Terrorism 24 (2001): 159–181.
Alex P. Schmid and A. J. Jongman, Political Terrorism: A New Guide to Actors, Authors, Concepts, Databases, Theories and Literature (Amsterdam: North-Holland Publishing Company, 1988).
A. J. Jongman, “Trends in International and Domestic Terrorism in Western Europe, 1968–88,” in A. P. Schmid and R. D. Crelinsten, eds., Western Responses to Terrorism (London: Frank Cass, 1993), 28.
Ibid., 28.
This figure is based on the available GTD as of September 29, 2006. Because the data base is being continuously updated, numbers change somewhat with successive revisions.
Although the original PGIS data from 1993 were lost, we were able to reconstruct totals for major categories from a PGIS report for 1993.
We recognize that the relatively small number of recorded incidents from 1970 through 1976 could be in part a consequence of the fact that PGIS data collectors simply invested fewer resources in data collection during the early years of data collection. Based on an analysis of the data, we do know that the early data are based on fewer recorded sources than the later data. Thus, for the year 1970, PGIS only reported 6 different sources, but by 1977 they reported 53 separate sources. However, this assessment is further complicated by the fact that PGIS data collectors frequently excluded their sources in the early years—68% of the cases in 1970 and 42% in 1977 included no sources. We should also point out that media-related information sources also increased dramatically during this period, especially media penetration of the industrializing world, which might account for at least part of the increase in rates since 1970.
The composition of countries within each region was determined by PGIS.
Mexico is counted here as part of Latin America instead of North America.
For convenience, we treat Northern Ireland here as a country.
Mischelle van Brakle, “What Happens When Terrorists ‘Win’?,” paper presented at the annual meetings of the American Society of Criminology, Los Angeles (2006).
Laura Dugan, Gary LaFree, and Alex R. Piquero, “Testing a Rational Choice Model of Airline Hijackings,” Criminology 43 (2005): 1031–1065.
Gary LaFree, Raven Korte, and Laura Dugan, “Deterrence and Defiance Models of Terrorist Violence in Northern Ireland, 1969 to 1992,” unpublished manuscript, START Center, University of Maryland, 2006.
Laura Dugan, Julie Huang, Gary LaFree, and Clark McCauley, “Sudden Desistance from Terrorism: The Armenian Secret Army for the Liberation of Armenia and the Justice Commandos of the Armenian Genocide,” unpublished manuscript, START Center, 2006.
Piyusha Singh, Laura Dugan, Gary LaFree, and Min Xie, “Spatial Patterns and Diffusion of Terrorism in Spain,” unpublished manuscript, START Center, 2006.
Laura Dugan and Gary LaFree, “Determinants of Global Terrorism Incidents,” paper presented at the annual meeting of the American Society of Criminology, Los Angeles, 2006.
Robert Greenbaum, Laura Dugan, and Gary LaFree, “The Impact of Terrorism on Italian Employment and Business Activity,” Urban Studies, forthcoming 2007.