Nonproportional hazards and event history analysis in international relations

Event history models have become a dominant method of analysis in the study of international relations. Conventional event history models, however, retain the assumption that the effects of the covariates remain proportional to each other throughout the duration of the subject's phase. Nonproportional hazard (NPH) models are used, which allow for the effects of covariates to vary over time. These models are then applied to three previously established data sets on the duration of postwar peace, civil wars, and alliances. Results show that NPH analysis is a useful method for testing new hypotheses, as well as removing possible sources of bias from existing analyses.