The Democratic Peace: Weighing the Evidence and Cautious Inference

The greater peacefulness of jointly democratic pairs of states is an important finding in research on the causes of war. Here, we outline a set of criteria for evaluating critiques of such robust empirical associations and apply them to two recent articles. Mousseau (2013) claims that contract-intensive economies, as proxied by a measure of life insurance expenditure, account for the democratic peace. However, his research suffers from various problems of analysis and interpretation, including a miscoded dependent variable, a misleading specification for dyadic democracy, a suppression of heterogeneous associations, and a heavy dependence on imputation in which greater than 90% of the values of the central independent variable were (improperly) imputed. We estimate 144 specifications that build from Mousseau's models and control for life insurance expenditures, finding substantial, robust support for the democratic peace. Gartzke & Weisiger (2013) claim that the importance of the democratic peace has declined as the proportion of democracies in the international system has increased; but their tests are misspecified and do not address the issue they raise. There are also serious errors in their data. When these problems are corrected, we find that the peacefulness of democratic pairs has actually increased as the proportion of democracies grew after 1816.双边民主国家对（jointly democratic pairs）具有更强的和平性，这是战争成因研究领域的一项重要发现。本文首先梳理出一套用于评估此类稳健经验关联之批判观点的标准，并将其应用于两篇近期研究文献。穆瑟（Mousseau，2013）提出，以人寿保险支出作为代理变量的契约密集型经济体，是民主和平论（democratic peace）的成因。然而，其研究存在诸多分析与解读层面的问题：包括因变量编码错误、双边民主的计量设定存在误导性、掩盖了异质性关联，以及严重依赖统计插补（imputation）——其中核心自变量超90%的数值被不当插补。我们基于穆瑟的模型构建了144种计量设定，并控制了人寿保险支出变量，最终发现民主和平论得到了显著且稳健的实证支持。加茨克与韦西格（Gartzke & Weisiger，2013）主张，随着国际体系中民主国家占比的提升，民主和平论的重要性有所下降；但其检验存在计量设定错误，且未回应其提出的核心议题，同时其数据也存在严重错误。在修正这些问题后，我们发现：自1816年以来，随着民主国家占比的增长，双边民主国家对的和平性实际上有所增强。