COW International Governmental Organization (IGO) Data (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):

Bibliography Entry: Pevehouse, Jon C., Timothy Nordstrom, and Kevin Warnke. 2004. "The COW-2 International Organizations
Dataset Version 2.0," Conflict Management and Peace Science 21(2):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(2):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 SPSS or Stata (for instance, use Stata’s “insheet” command) to correctly access the full data. Data on IGOs from 1815-2005, at the IGO-year level. Contains one record per IGO-year (with years listed at 5 year intervals through 1965, and annually thereafter). Data on IGOs from 1815-2005, at the country-year level. Contains one record per country-year (with years listed at 5 year intervals through 1965, and annually thereafter). (40 Megabytes) Data on IGOs from 1815-2005, at the dyad-year level. Contains one record per dyad-year (with years listed at 5 year intervals through 1965, and annually thereafter). (18 Megabytes) Data on IGOs from 1815-2005, at the dyad-year level (as in, but with the data file saved in Stata format (.dta) rather than as a comma-delimited (.csv) file.
IGO_codebook_v2.1.pdf Main codebook for the IGO data set, describing file formats, variable values, and listing variables contained in the component data files.
IGO_overview_of_changes_in_v2.3.pdf A .pdf file that provides a unit specific explanation of the changes made in v2.3.



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.

A slightly different version of the data set appeared in the 1970 article listed above. This version is designated 1.1. Those interested in seeing a listing of the IGOs included in version 1.1 of the data should visit IGOs (1.1).

Existing documentation concerning the original IGO collection can be found 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 Megan Shannon (University of Mississippi) under the COW 2 Data Set Hosting Program. Please report all suspected errors or anomalies to the authors at, and . Further details on the data sets and coding procedures may be obtained from the authors.