Common Interests or Common Polities? Reinterpreting the Democratic Peace

The central claim of a rapidly growing literature in international relations is that members of pairs of democratic states are much less likely to engage each other in war or in serious disputes short of war than are members of other pairs of states. Our analysis does not support this claim. Instead, we find that the dispute rate between democracies is lower than is that of other country pairs only after World War H. Before 1914 and between the World Wars, there is no difference between the war rates of members of democratic pairs of states and those of members of other pairs of states. We also find that there is a higher incidence of serious disputes short of war between democracies than between nondemocracies before 1914. We attribute this cross-temporal variation in dispute rates to changes in patterns of common and conflicting interests across time. We use alliances as an indicator of common interests to show that cross-temporal variation in dispute rates conforms to variations in interest patterns for two of the three time periods in our sample.