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International Organization v2.3


The IGO data sets contain information about intergovernmental organizations (international organizations that have at least 3 nation-states as their members) from 1815-2005. The IGO data are collected at 5-year intervals from 1815-1965, and annually thereafter. The data are presented in three forms with distinct units of analysis. Form 1 is organized by IGO, listing all IGOs with the IGO-year as the unit of analysis, and identifying all state members of the IGO in that year. Form 2 is organized by state, listing all states with the country-year as the unit of analysis, and identifying all IGO memberships of the state in that year. Form 3 combines individual country memberships into joint dyadic memberships in each IGO, marking joint membership in each IGO for each pair of states. The expanded version 2.3 updates the original Wallace and Singer (1970) data set to provide membership information from 1964-2005, along with recoding some earlier IGOs.


In any papers or publications that utilize this data set, users are asked to give the version number and cite the documentation for the data set, as follows (this citation will be replaced by the article of record for the data set when information is available):


Pevehouse, Jon C., Timothy Nordstrom, and Kevin Warnke. 2004. "The COW-2 International Organizations Dataset Version 2.0," Conflict Management and Peace Science 21:101-119.

The original IGO data set was collected by Michael Wallace and J. David Singer and is described in


Wallace, Michael, and J. David Singer. 1970. "International Governmental Organization in the Global System, 1815-1964." International Organization 24: 239-87. 

Data Set

Version 2.3 comprises three different data sets plus documentation; each data set has a different unit of analysis. In each version, data through 1965 are coded at 5 year intervals in keeping with Wallace and Singer (1970), while data after 1965 are coded annually. 496 IGOs are coded in the data.


The data are distributed as individual ZIP files along with the codebook/coding manual, which together make up the data set and documentation. The data sets are distributed (within each zip file) in comma-delimited format; the first line of each data file contains the variable names. Because of the size, we have also made the data available in .dta format.


Note that these are large data sets in comma-delimited ascii format, with values separated by commas and ending in a .csv extension.  By default in Microsoft Windows, files with a .csv extension will open in Microsoft Excel.  However, Excel limits the size of spreadsheets. The state and dyad-level files contain too much data for Excel, and so Excel will only read part of the data set.  To use these datasets, you should use a statistics program such as Stata (for instance, use Stata’s “insheet” command) to correctly access the full data.


Version 2.3 of the IGO data replaced version 2.1 on June 30, 2010. It expands the data from v2.1 until 2005.


Earlier Versions

Version 1.0 of the IGO data may be obtained from the Inter-university Consortium for Political and Social Research (ICPSR) as study number 5520 (Intergovernmental Organization Data, 1816-1964 ). The abstract of the data set may be viewed by clicking here.

Questions and Feedback

Version 2 of the IGO data set is hosted by Timothy Nordstrom (University of Mississippi), Jon Pevehouse (University of Wisconsin) and  (Colorado-Boulder) under the COW Data Hosting Program. Please report all suspected errors or anomalies to the authors. Further details on the data sets and coding procedures may be obtained from the authors.