The Role of Social Networks in the Evolution of Al Qaeda-inspired Violent Extremism in the United States, 1990-2014 (ICPSR 36235)

Version Date: Sep 30, 2021 View help for published

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Jytte Klausen, Brandeis University

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This study compiled data on American jihadists and other Islamic extremists recruited since the early 1990s. Specifically, "homegrown" terrorist, referring to Americans and other Westerners who are inspired to commit acts of terrorism or support those committing these acts in their home country on behalf of foreign terrorist organizations, are the main focus. The purpose of this research is to address the central question: How do foreign terrorist organizations mobilize Americans to carry out attacks on their behalf?

Variables collected include extremist group affiliation, criminal background, foreign fighter history if applicable, coconspirators and their relationship, and the location and nature of terrorist plots. Demographic variables include sex, ethnicity, immigration status, education, and profession.

Klausen, Jytte. The Role of Social Networks in the Evolution of Al Qaeda-inspired Violent Extremism in the United States, 1990-2014. Inter-university Consortium for Political and Social Research [distributor], 2021-09-30.

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United States Department of Justice. Office of Justice Programs. National Institute of Justice (2012-ZA-BX-0006)


This data collection may not be used for any purpose other than statistical reporting and analysis. Use of these data to learn the identity of any person or establishment is prohibited. To protect respondent privacy, this data collection is restricted from general dissemination. To obtain this file, researchers must agree to the terms and conditions of a Restricted Data Use Agreement in accordance with existing ICPSR servicing policies.

Inter-university Consortium for Political and Social Research

1990 -- 2014
2013 -- 2016

This project was undertaken to study how Western homegrown jihadist terrorists are mobilized to act on behalf of, or support Al Qaeda-inspired extremists. The central question was how do foreign terrorist organizations mobilize Americans to carry out attacks on their behalf? Five additional questions were addressed. What is the role of networks and organizations in mobilizing and channeling Americans for jihadist action? What are the structural characteristics of the American Islamist extremist networks? How integrated are those domestic networks with the global Islamist extremist movement and with the core leadership of Al Qaeda and other foreign terrorist organizations? How do jihadist leaders balance conflicting organizational objectives? What role does internet-based proselytizing and recruitment play in stimulating homegrown terrorism?

The data was collected as part of the Western Jihadism Project (WJP), which was initiated in 2006, and based out of Brandeis University. The term homegrown terrorism came into use in 2005, following the Madrid train bombings from March 11, 2004 and the London Underground bombings from July 7, 2005. Evidence seized during a raid in Abbottabad, Pakistan during May 2, 2011 showed that Al Qaeda associates and Osama Bin Laden centrally directed these attacks. Then, in 2014, a fraction of Al Qaeda in Iraq broke away to form the Islamic State (ISIL). In Europe, attackers who returned from Syria on orders of ISIL committed acts of terror. Meanwhile, the gunmen who launched the San Bernardino and Orlando attacks claimed allegiance to ISIL, but had no direct contact with ISIL. These and other infamous terrorist incidents motivated the demand for research to understand the changing nature of terrorism, and the perceived threat of the homegrown terrorist phenomenon in particular.

Homegrown, as defined above, implies that radicalization occurred while the individual lived in the United States or another Western democracy. It does not include domestic terrorism which lacks an international dimension, such as anti-abortion terrorism, or eco-terrorism. "Foreign fighters", who go abroad to fight with jihadist groups in a country of which they are not citizens and have no known relationship of any other kind, are often identified as homegrown, but this is context dependent. Individuals from Muslim majority countries who come to the United States to carry out an attack are not considered homegrown. Based on these criteria, approximately 700 unique persons, 500 of which were inspired by Al Qaeda and roughly 200 acted on behalf of Hamas, Hezbollah, or the Palestinian Islamic Jihad, were included in the analysis

Social network analysis (SNA) was used to study the relationships these individuals have with individuals and organizations involved with terrorism. SNA provides users with visualizations of the social relationships individuals hold and data for further inquiry. Data used was collected as part of the WJP database. Clio-metrics, the quantitative analysis of micro-level data derived from narrative records, was used to further analyze these 700 cases. Three primary data sources were utilized: primary sources such as court records, indictments, judgments; reports published by government researchers or academic teams; and communications issued by extremists, such as testimonies, social media, and websites.

A codebook was developed to help researchers record terrorist-related actions. This included communication between terrorists and between offenders and terrorist organizations, such as foreign terrorist groups, web sites, and extremist mosques. Relationships were coded to indicate if the relationship was symmetrical or asymmetrical. Demographic information was included in coding as well.

Longitudinal: Cohort / Event-based

American nationals associated with jihadist terrorist plots related to Al Qaeda and aligned groups, from the early 1990s to the end of 2014.


The American Dataset holds background information on all study participants, and the terrorist group they're affiliated with. Country of terrorist plot, as well as country of citizenship, residency, and death are included. Criminal background is listed as well. Demographic variables include sex, ethnicity, immigration, education, and occupation.

The Foreign Fighters Dataset contains those individuals who have attempted or participated in extremist activity abroad. This is determined by participants coded as "Death," "Participation," or "Attempt" for the variable FOREIGNFIGHTER in the American Dataset. The location, year, and whether or not the foreign fighter attempt was successful are recorded. Additional variables include if the individual is deceased, imprisoned, and if they engaged in a suicide operation.

The People Links Dataset tracks known connections between individuals from the American Dataset. The person who is more dominant is listed to the far left. An additional variable capturing the nature of the relationship is coded for.

The Events and Organizations Links Dataset lists known links that individuals have to terrorist incidents. The nature of the event or organization type affiliated with the event is included. The name of the organization or event and the individuals link to it is recorded.

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