Measuring Space: A Minimum-Distance Database and Applications to International Studies

In this overview of a new database and approach to measuring distance among historical and contemporary independent nation-states, we review the utility of space to theory and empirical research in international studies. We identify weaknesses in existing empirical data on distances and contiguity among nations. Categorical data on distance treat proximity as an either-or issue and do not permit identifying degree of proximity among states. Continuous measures of distances between midpoints, such as capital cities, often overstate the actual distances between state borders and suffer for large states and irregular territories. We outline a new alternative approach, based on measuring the minimum distance for pairs of polities in the international system, which remedies some of these shortcomings. The current implementation of the minimum-distance database includes the minimum distances for all polities within 950 km of each other from 1875 to the present. We demonstrate the enhanced flexibility of the new minimum-distance approach relative to existing alternatives. Moreover, we illustrate how variables constructed from distance measures, combined with spatial statistical techniques, can contribute substantively to international relations and cross-national comparative research. We demonstrate the importance of dependence among geographical neighbors by examining the link between levels of economic wealth and prospects for democracy in the context of regional interdependence among states.