How do leaders shape, and how are they shaped, by international relations? What drives a leader to travel from one country to another or to any other place in the world? What can we learn about travel, trade, conflict, diplomacy, democracy, and other interconnected systems by researching the travel patterns of country and organization leaders? These central questions drive the Pardee Institute’s decade-long COLT (Country and Organization Leader Travel) project, which the U.S. Government sponsors.  

The Pardee Institute explored these and related research questions for an audience of faculty, students, and staff from the University of Denver’s Josef Korbel School of Global and Public Affairs (the Korbel School) during its first-ever Lunch and Learn seminar. 

Following an introduction of the COLT dataset and Lunch and Learn series by Pardee Institute Director Jonathan Moyer, Pardee Institute COLT Program Manager Kylie McKee, and Director of Analysis Collin Meisel took turns presenting on different facets of the COLT project.  

The COLT project captures data on Heads of Government and State (HOGS) travel from 1990 through the present day for 212 countries and territories. This scale of data collection requires large-scale infrastructure and staff, from coders to vetters to team leads (all positions held by students), until ultimately the data reaches McKee and Meisel.  

This dataset tracks over 43 variables and 70 biographical variables for each leader, creating an extensive dataset that requires countless hours to track and ensure accuracy, McKee described. McKee went on to detail her team’s research protocol: monthly updates to the data, as well as annual public reports, made possible by weekly tracking of HOGS travel, reviews of data for errors and/or gaps, and extensive final reviews. This work is divided into four groups of RAs who research HOGS from specific regions of the world. 

In Meisel’s words, the COLT dataset is not trying to prove cause and effect; it is trying to see “what moves together.” Meisel, McKee, and their team of student researchers have found the frequency and destination of world leader visits correlate strongly with material interests (such as trade, arms deals, and foreign aid), institutional co-membership (like NATO or the EU), and patterns of conflict. This research matters because diplomatic travel provides a high-frequency, actionable indicator of shifting geopolitical affinities and power dynamics. 

Another question that the COLT project is attempting to tackle is the puzzle of leader travel. With all the modern advances in technology —from phone calls to video conferencing —along with the time and potential dangers involved in traveling, what are the benefits of leaders traveling abroad to meet with other leaders in person? The literature suggests that travel plays a significant role in shaping leader opinions, as seen in trade and relationships between HOGS, Meisel explained. However, most of this literature is focused on one country or a region of the world. The COLT project addresses a major missing piece of the puzzle – its scope is global, making it truly unique and a flagship project for this sort of data collection. 

Because the data is so exhaustive, it can be challenging to know for sure how much of it is captured by the researchers—is it simply the tip of the iceberg, with much concealed beneath the surface, or is most of it visible to these teams? To address these demands, McKee answered that the teams on Pardee’s COLT project are always innovating their methods and processes so that the data can be better used as a resource and source of lessons for future data gathering. For example, McKee shared that Pardee will soon use AI to streamline its data by gathering qualitative information in a systematic format for analysis. 

The event ended with a question-and-answer portion, filled with questions ranging from the use of the data set as a diagnostic tool to which regions have the most tracked travel to if the project had any student position openings. Other questions addressed the uses of AI, how the COLT data is utilized, and where it is sourced.  

To learn more about the COLT Project, access the COLT data, or read the COLT analysis published in International Studies Quarterly, click here.  

This inaugural Lunch and Learn event is part of a new series of Pardee-hosted lunchtime seminars designed to inform the broader Korbel School community about the research approach and applications of the Pardee Institute's work. 

By: Sylvia Morna Freitas

International Studies Quarterly published a new article authored by Institute Director Jonathan D. Moyer, Acting Director of Analysis Collin J. Meisel, COLT Project Manager Kylie X. McKee, and a larger team of researchers, making the Country and Organizational Leader Travel (COLT) dataset public for the first time. The COLT dataset is a research project at the Frederick S. Pardee Institute for International Futures that documents the travel of heads of government and state (HOGS) from 212 different countries from 1990 through 2024. The COLT dataset is the first of its kind. Accounting for 78,641 foreign trips as of 2023, the article delves into how the comprehensive and global nature of the dataset allows for “the first generalizable findings on the causes and effects of global leader travel.”  

In their ground-breaking article on the COLT dataset, the authors demonstrate the utility of the data through a series of statistical tests. First, they provide descriptive statistics about trends in HOGS travel over time. Second, they test the drivers and correlates of travel and use the analyses to evaluate causal relationships between leader travel and a variety of other factors. And third, they conduct a special exploration of the relationship between travel and trade with the first global dataset.    

The country-level annual net in-visits minus out-visits averaged from 1990 to 2023 with higher values indicating more net in-visits. Source: Moyer et al. June 2025. "When Heads of Government and State (HOGS) Fly: Introducing the Country and Organizational Leader Travel (COLT) Dataset Measuring Foreign Travel by HOGS", International Studies Quarterly, Volume 69, Issue 2.

Digging into the richness of the data, the authors highlight several interesting trends for the 1990-2023 period. For example, leaders averaged 10.9 international trips per year, and despite a significant decline in travel due to COVID-19, by 2023, leader travel reached a post-1990 high with 3,188 total trips occurring that year. The United States and European countries received the most visits, while countries like Palestine visited the most countries, and the African region had the fastest annual growth rate for visits at 4.5 percent. From the data, the authors found that democracies tend to travel more than autocracies, although there is significant variation at the country level. Additionally, countries with higher diplomatic influence, such as those in the European Union or North Atlantic Treaty Organization, received a disproportionate share of visits. 

The authors were then able to test theories about drivers of leader travel from previous research with a global dataset for the first time. “Our findings reinforce many explanations of what drives leader travel, showing that levels of development, material capabilities, economic and institutional interdependencies, conflict, distance, and homophily all matter,” the authors say in the article.  

Their analysis came to these conclusions by examining both monadic (country-year) and dyadic (country-pair-year) models. The findings show that material interests are a key factor influencing leader travel, with countries involved in economic exchanges—such as fossil fuel exports, foreign aid, and arms trade—experiencing more visits. Additionally, states involved in conflict are more likely to engage in diplomatic travel, possibly as part of efforts to manage or resolve conflicts. Another significant factor is the logic of homophily, where leaders tend to visit countries with similar political values or regime types, with shared voting behavior in the UN also correlating with more frequent bilateral visits. Geographical distance also plays a crucial role with greater distance between countries leading to fewer trips due to the increased costs of travel. In addition, the routine and reciprocal nature of visits is important, with regular diplomatic exchanges leading to more frequent travel.  

Overall, the authors findings demonstrate that diplomatic travel is driven by a combination of economic, political, and geographical factors that have been explored in past literature but can now be interrogated and probed more deeply with the COLT data. For example, prior literature claims “an increase in diplomatic travel is a leading indicator of increased trade.” The authors were able to test the robustness of this claim by testing the relationship between travel and trade across COLT’s global dataset, instead of just the two countries, China and the U.S., that the original study was based on. The authors find that while leader travel is a leading indicator of increased trade, increased trade is also a leading indicator of increased travel. In other words, the causal relationship is complex and bidirectional. 

The authors of the COLT project were motivated to create this dataset because of the under-investigation this topic has received in the past. Despite literature that highlighted the importance of HOGS visits vis-a-vis a variety of diplomatic factors, earlier studies were often limited to western or powerful countries, overlooking smaller, non-western states and limiting the reach of conclusions drawn on the causes and effects of leader travel. This previously unaddressed gap is where the COLT dataset is making a unique contribution. As the first public-access resource of its kind, the COLT dataset will further future research on “issues such as national prestige, public diplomacy, weaponized interdependence, and interstate conflict.” 

The COLT dataset is the product of several years of dedicated work from the authors of the new article and hundreds of undergraduate and graduate research aides at the Pardee Institute. A large part of what makes it possible for the COLT dataset to be so extensive is the large team of student employees that actively track and code new leader trips. Participation in the project also gives students at the University of Denver a unique opportunity to expand their professional and data management skills. The cross-sectional nature of COLT’s team, from the Pardee Institute’s director to undergraduate research aides, is indicative of the Institute’s wider innovative approach to generate useful research and help develop a new generation of experienced professionals in the field. 

The COLT dataset and codebook are freely available to the public and are included with the replication materials accompanying the article in the International Studies Quarterly. To access the dataset, click here. To read the full article, click here. 

COLT is part of the Institute’s Diplometrics Program. Diplometrics is funded by the U.S. government to better understand and measure relationships in the international system by gathering data, building tools, and conducting analysis. The project identifies international interactions that measure the depth and breadth of political, diplomatic, economic, security, and cultural ties between countries. The results and views expressed are those of the authors alone and do not represent the views of the U.S. Government. 

Moyer, J., Meisel, C., Szymanski-Burgos, A., Scott, A., Casiraghi, M., Kurkul, A., Hughes, M., Kettlun, W., McKee, K., Matthews, A., (2025, March 17). When heads of government and state (HOGS) fly: Introducing the country and organizational leader travel (COLT) dataset measuring foreign travel by HOGS. International Studies Quarterly, Volume 69, Issue 2, June 2025, sqaf013, https://doi.org/10.1093/isq/sqaf013

Despite representing a crucial day-to-day diplomatic tool, travel by heads of government and state (HOGS) has remained an under-investigated topic in international relations, inhibiting our ability to better understand how these visits change foreign aid, interstate conflict, diplomatic affinities, and more. Here, we fill that gap by introducing the first global dataset on the foreign visits of state leaders, the Country and Organizational Leader Travel (COLT) dataset, which allows us to present descriptive analysis and assess the monadic and dyadic drivers of foreign travel by HOGS. We find evidence consistent with previous literature explaining the motives of leader travel: development, trade, conflict, institutional co-membership, and regime type. In addition, we show a potential further application of the dataset, presenting original results on the relation between diplomatic visits and international trade. Overall, these data represent a unique indicator of international interaction that cuts across levels of analysis.