The democratic peace—the idea that democracies rarely fight one another—has been called “the closest thing we have to an empirical law in the study of international relations.” Yet, some contend that this relationship is spurious and suggest alternative explanations. Unfortunately, in the absence of randomized experiments, we can never rule out the possible existence of such confounding biases. Rather than commonly used regression-based approaches, we apply a nonparametric sensitivity analysis. We show that overturning the negative association between democracy and conflict would require a confounder that is forty-seven times more prevalent in democratic dyads than in other dyads. To put this number in context, the relationship between democracy and peace is at least five times as robust as that between smoking and lung cancer. To explain away the democratic peace, therefore, scholars would have to find far more powerful confounders than those already identified in the literature.

中文翻译：

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民主和平经验证据的稳健性：非参数敏感性分析

民主和平——民主国家很少互相争斗的想法——被称为“我们在国际关系研究中最接近经验法则的东西”。然而，有些人认为这种关系是虚假的，并提出了其他解释。不幸的是，在没有随机实验的情况下，我们永远不能排除这种混杂偏差的可能存在。我们应用了非参数敏感性分析，而不是常用的基于回归的方法。我们表明，要推翻民主与冲突之间的负面关联，需要一个混杂因素，这种混杂因素在民主二元组中的流行率是其他二元组的 47 倍。把这个数字放在上下文中，民主与和平之间的关系至少是吸烟与肺癌之间关系的五倍。