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Correlates of War Project

Paul Diehl - Current Director
University of Illinois
Dept. of Political Science
361 Lincoln Hall
702 S. Wright St. Urbana, IL 61801

The Correlates of War Project was founded in 1963 by J. David Singer, a political scientist at the University of Michigan. The original and continuing goal of the project has been the systematic accumulation of scientific knowledge about war. Joined by historian Melvin Small, the project began its work by assembling a more accurate data set on the incidence and extent of inter-state and extra-systemic war in the post-Napoleonic period. To do this scientifically Singer and Small found they needed to operationally resolve a number of difficult issues such as what is a "state" and what precisely is a "war." Building upon the work of other pioneers such as Pitirim Sorokin, Lewis Frye Richardson, and Quincy Wright, Singer and Small published The Wages of War in 1972, a work that established a standard definition of war that has guided the research of hundreds of scholars since its publication.

This publication was only the beginning of the project, for the fundamental goal of the project was not just to measure the temporal and spatial variation in war but rather to identify factors that would systematically explain this variation. Accordingly, early efforts were undertaken to measure many of those factors that purportedly accounted for war such as national capability, alliances, geography, polarity, and status in the post-Napoleonic period, and the list of data sets assembled by the project has continued to grow over the years (see Data Sets). In addition to the collection of data, the project has conducted many empirical studies (see Bibliographic Essay) about war and conflict. An important progeny of the project is the BCOW (Behavioral Correlates of War) headed by Russell Leng. Through the years, the project has served as a major training ground for young scholars, and many of today’s best known and widely respected international relations scholars are "products" of the project. More generally, the correlates of war project promoted cumulative science in the field of international relations when the scientific study of politics was in its infancy. By helping to establish a clear temporal and spatial domain for research, promoting the use of clearly defined concepts and common variable operationalizations, and allowing replication of research, the project has been a mainstay of rigorous international relations scholarship.

In the late 1990s scholars became concerned about how the work of the project could be continued given the pending retirement of J. David Singer, and arrangements were made to transfer the project to Penn State under the leadership of Stuart A. Bremer. This transfer was marked by a March, 2001, conference discussing the future study of war, held at Penn State. Penn State has archived all available original material from the Correlates of War project, and is extending and enlarging the data collection efforts it began.

As of November, 2002, the project continues under the leadership of Interim Director D. Scott Bennett, and Associate Director Glenn Palmer. As of January 2005, the project continues under Director Paul
Diehl, and Associate Director D. Scott Bennett.

Participating Institutions: International Alliances: Doug Gibler, University of Kentucky - Intergovernmental Organizations: Timothy Nordstrom, University of Mississippi; John Pevehouse, University of Wisconsin - Territorial Change: Paul Diehl, University of Illinois - Direct and Colonial Contiguity: Paul Hensel, Florida State University - Interstate and Extrastate War: Meredith Sarkees, Saint Mary's University; Frank Wayman, Wayne State University - Intrastate War: Jeff Dixon, Wright State University; Meredith Sarkees, Saint Mary's University. - Culture: Errol Henderson, Penn State University - Militarized Disputes: Glenn Palmer, Penn State University

Advisory Board / Host Liaisons: International Alliances: James Ray, Vanderbilt University - Intergovernmental Organizations: Brian Pollins, The Ohio State University - System Membership: Paul Diehl, University of Illinois - Geopolitical Units: Paul Diehl, University of Illinois - Interstate, Intrastate, and Extrastate War: Paul Hensel, Florida State University - Culture: James Ray, Vanderbilt University - Militarized Disputes: Brian Pollins, The Ohio State University

Objectives: The Correlates of War project seeks to facilitate the collection, dissemination, and use of accurate and reliable quantitative data in international relations.

Key principles of the project include a commitment to standard scientific principles of replication, data reliability, documentation, review, and the transparency of data collection procedures.

More specifically, we are committed to the free public release of data sets to the research community, to release data in a timely manner after data collection is completed, to provide version numbers for data set and replication tracking, to provide appropriate dataset documentation, and to attempt to update, document, and distribute follow-on versions of datasets where possible. We intend to use our website as the center of our data distribution efforts, to serve as central site for collection of possible error information and questions, to provide a forum for interaction with users of Correlates of War data, and as a way for the international relations community to contribute to the continuing development of the project.

Ongoing Research: The Correlates of War project seeks to expand available data for IR research in two ways. First, we have a number of projects ongoing "in house." Second, we are encouraging scholars within the Correlates of War community to engage in guided research through the Data Hosting Program. This page lists projects and activities ongoing under the COW rubric.

Highest Priority:  Dyadic War Data: We are currently working to identify, in each multilateral interstate war, which states actually engaged each other militarily, and at what level of violence (e.g. did not interact, declared war, had air/ground combat only, engaged each other extensively). Work proceeding in conjunction with Resat Bayer, Koc University and College of Wooster.

Lower Priority:  Diplomatic Relations: Patterns of diplomatic representation tell us a lot about the status ordering and lines of communication in the interstate system. Beginning in 1817, information about diplomatic bonds between states at 5-year intervals is contained in this data set.

Geopolitical Units: While a key element of the international system since 1816, formal and recognized states have not always covered the globe in the manner they largely do today. This data set traces the status of non-state territorial units in the system, including colonies, mandates, autonomous territories, and so on, their relationship, and their eventual incorporation in/transformation to states.

Ongoing hosted projects:  Cultural Attributes of States: Cultural differences between and within states are thought by some to contribute to conflict. In order to test these speculations a data set delineating the linguistic, religious, and ethnic composition of states was created. It records this information for all states at 10-year intervals from 1820 to 1990. Hosted by Errol Henderson, Penn State University.

Interstate/Extrastate War Data: We are currently working to update the interstate war data through 2003, through the auspices of data set hosts Meredith Sarkees, Saint Mary's University, and Frank Wayman, Wayne State University.

Intrastate War Data: We are currently considering updates, extensions, and some possible redefinitions in the intrastate war data, through the auspices of data set hosts Jeff Dixon, Wright State, and Meredith Sarkees, Saint Mary's University.

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