When HOGS Fly: Pardee’s Newest Dataset Spreads its Wings

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.    

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.