Frequently Asked Questions

Why doesn't GTD have a set definition of terrorism?
I came across an incident in the database that I do not believe is terrorism. Why was it included?
I found a factual error or a case missing from the database. How did this happen?
Does the GTD include foiled and failed plots or threats to attack?
Does the GTD include incidents of state terrorism?
Who makes the decisions about what to include as an incident?
How do I get access to the raw data?
Who funds the database?
Why are the data for 1993 missing?
Is there a methodological reason for the decline in the data between 1997 and 1998?

Why doesn't GTD have a set definition of terrorism?

In the absence of a universally accepted definition of terrorism, GTD uses various coded criteria to cover a broad range of definitions of terrorism through a combination of inclusiveness and filtering. The goal is to have a data set that is useful to as many interested users as possible.

Please see our Methodology Page and GTD Codebook for more details.

I came across an incident in the database that I do not believe is terrorism. Why was it included?

While the GTD inclusion criteria offer a comprehensive definition of terrorism, we encourage users to take advantage of the GTD's flexibility to restrict the data according to their definitional preferences. This includes filtering search results based on whether the coder noted some uncertainty whether an incident meets all of the criteria for inclusion ("Doubt Terrorism Proper," available for post-1997 cases only). Also, users can filter search results based on which of the following three criteria are met (available for all cases):

Criterion I: The act must be aimed at attaining a political, economic, religious, or social goal.
Criterion II: There must be evidence of an intention to coerce, intimidate, or convey some other message to a larger audience (or audiences) than the immediate victims.
Criterion III: The action must be outside the context of legitimate warfare activities.

Please see our Methodology Page and GTD Codebook for more details.

I found a factual error or a case missing from the database. How did this happen?

While every effort is made for each incident to corroborate facts from multiple independent sources and to eliminate errors through a systematic review process, the magnitude of the database (over 80,000 discrete incidents) means that occasionally an error will evade detection and appear in the database or a valid incident will not be recorded. In these cases, we rely on users who become aware of such an error to contact us and let us know.

Does the GTD include foiled and failed plots or threats to attack?

Although the GTD does include failed attacks, it does not include foiled or failed plots, the distinction being that the attack must actually be attempted to qualify for inclusion in the database. Likewise, the GTD does include attacks in which violence is threatened as a means of coercion, but does not include threats to attack where no action is taken.

Does the GTD include incidents of state terrorism?

No, the GTD is limited to acts of non-state terrorism. One of the three necessary criteria for inclusion is that there must be sub-national perpetrators.

Please see the GTD Codebook for more details.

Who makes the decisions about what to include as an incident?

The basic criteria were formulated by the GTD Advisory Board, and were reflected in the data collection process. In practice, individual data collectors decide whether a case they are working on fulfills these criteria, and this decision is reviewed by GTD supervisory staff. In cases where determination is difficult, the decision is made by the senior GTD management. If uncertainty persists, exceptionally difficult cases can be referred to the GTD Advisory Board for discussion and adjudication.

How do I get access to the raw data?

United States government officials and interested researchers can request a copy of the GTD data files from the March 2009 release through the GTD Contact Form.

Users can also access previous versions of GTD1 and GTD2 data through the Terrorism and Preparedness Data Resource Center (TPDRC)—a joint project of START and the University of Michigan's Inter-University Consortium for Political and Social Research (ICPSR). The links below direct users to data files, codebooks, and supporting materials for:

GTD1 (cases from 1970 to 1997) (TPDRC Study #22541)
GTD2 (cases from 1998 to 2004) (TPDRC Study #22600)

Please join the START mailing list to receive a notification when more recent versions of the data become available.

Who funds the database?

The initial collection of GTD data was performed by the Pinkerton Global Intelligence Services (PGIS) between 1970 and 1997 and was donated to the University of Maryland. Subsequent work on GTD1 was funded by a grant from the National Institute of Justice (NIJ2002-DT-CX-0001) and thereafter as part of the START Center of Excellence by the Department of Homeland Security Science and Technology Directorate (DHS S&T), Office of University Programs (Grants #N00140510629 and 2008-ST-061-ST0004). Funding for GTD2 was supplied by the DHS S&T Human Factors Division under contract #HSHQDC-05-X-00482. All information in the database on events through 2007 was collected and coded by database staff at the National Consortium for the Study of Terrorism and Responses to Terrorism (START) and the Center for Terrorism and Intelligence Studies (CETIS). The GTD does not purport to represent the official position, inclusion decisions, or information holdings of the Department of Homeland Security, the National Institute of Justice, or any other funding agency.

Why are the data for 1993 missing?

The original PGIS data, upon which the 1970-1997 GTD data are based, consisted of hard-copy index cards, which were subsequently coded electronically by START researchers. Unfortunately, the set of cards for 1993 was lost prior to PGIS handing the data over to START. Country-level statistics for 1993, including number of incidents, number of fatalities, number injured, number of U.S. fatalities, and number of U.S. injured were recovered from a PGIS Risk Assessment Report for 1993. These figures are available in the appendix of the GTD Codebook.

Is there a methodological reason for the decline in the data between 1997 and 1998?

While efforts have been made to assure the continuity of the data from 1970 to the present, users should keep in mind that the data collection was done as events occurred up to 1997, retrospectively between 1998 and 2007, and again concurrently with the events after 2008. This distinction is important because some media sources have since become unavailable, hampering efforts to collect a complete census of terrorist attacks between 1998 and 2007. Thus, users should note that differences in levels of attacks before and after 1997 are at least partially explained by differences in data collection; and researchers should adjust for these differences when modeling the data.