A universal test of an expected utility theory of war

Bueno de Mesquita and Lalman's version of an expected utility theory of war has become one of the most widely cited theories of international conflict. However, the testing of the theory has lagged behind its theoretical development. In its most sophisticated formulation, the theory has been tested on only 707 dyad-years, all drawn from Europe between 1816 and 1970. We present a test of the expected utility theory of war (as developed in War and Reason) on the international system from 1816 to 1984. Specifically, we examine the relationship between the main equilibrium variables derived under the "domestic variant" of the international interaction game and behavioral outcomes using multinomial legit. We find that the equilibria correlate with actual behavior in both the set of all dyads and a subset of politically relevant dyads, even after including a set of control variables. The relationship is somewhat less clear among the population of all interstate-directed dyads, however, with key equilibrium variables having smaller effects at increasing the odds of interstate conflict among all dyads. We also present a new software program, EUGene, which generates expected utility data and can serve as an important data management tool for international relations researchers.