Concentration, Polarity, and the Distribution of Power

Scholars of international relations generally rely on polarity to measure the distribution of power. I argue that another feature of this distribution—concentration—should be considered more carefully in analyses of international relations. Much of the recent literature on the distribution of power draws on analogies between the structure of markets and the structure of the international system. Concentration is more consistent than polarity with the microeconomic foundations of these studies. Further, using polarity to measure the distribution of power also requires analysts to assume (often implicitly) that: (1) inequalities among major powers are unimportant features of the global distribution of power; and (2) nonpolar major powers should be ignored in structural analyses of international relations. I maintain that these assumptions are at odds with many leading explanations of international relations. A number of prominent theories of balancing behavior, the onset of war, and the international political economy emphasize both the importance of both major (as well as polar) powers and the inequalities in power among them. As a result, analyses that center solely on the effects of polarity are likely to offer incomplete explanations of balancing behavior, the onset of war, and the international political economy. Since concentration measures both the number of major powers and the inequalities in power among them, these analyses may be enhanced substantially by considering the influence of concentration, as well as polarity.