Causes of Peace: Democracy, Interdependence, and International Organizations, 1885–1992

Previous studies provide strong evidence for the Kantian theory of peace, but a satisfactory evaluation requires establishing the causal influence of the variables. Here we focus on the reciprocal relations between economic interdependence and interstate conflict, 1885–1992. Using distributed-lags analyses, we find that economically important trade does have a substantively important effect in reducing dyadic militarized disputes, even with extensive controls for the influence of past conflict. The benefit of interdependence is particularly great in the case of conflict involving military fatalities. Militarized disputes also cause a reduction in trade, as liberal theory predicts. Democracy and joint membership in intergovernmental organizations, too, have important pacific benefits; but we find only limited support for the role of costly signals in establishing the liberal peace. We find no evidence that democratization increases the incidence of interstate disputes; and contrary to realists' expectations, allies are not less conflict prone than states that are not allied. Democracies and states that share membership in many international organizations have higher levels of trade, but allies do not when these influences are held constant.