Informal modes of cooperation are a central element of the complex institutional architecture of contemporary global governance. Collectively and individually, the contributions to this special issue broaden the emerging research on informal governance in world politics and provide novel empirical analyses based on unique data. In this introduction, we outline the research questions and puzzles that the special issue addresses. We then sketch three types of informality in world politics: Informality of institutions, within institutions, and around institutions. We discuss each type and provide examples from the contributions to the special issue and the existing literature. We consider how differentiating among these types of informality provides novel insights into the causes of informal global governance. We also identify candidate independent variables which, individually and in combination, should allow researchers to explain the striking variation in the growth and distribution of informal governance in world affairs. We summarize the main findings of the contributions and conclude by outlining an agenda for future research on informal governance in world politics.

非正式的合作模式是当代全球治理的复杂体制架构的核心要素。集体和个别地，对这一特刊的贡献扩大了世界政治中关于非正式治理的新兴研究，并基于独特的数据提供了新颖的经验分析。在本简介中，我们概述了本期特刊所涉及的研究问题和困惑。然后，我们概述了世界政治中的三种非正式性：制度的非正式性，制度内部的以及周围的机构。我们讨论每种类型，并提供对特刊和现有文献的贡献的实例。我们考虑将这些非正式形式之间的差异如何提供对非正式全球治理起因的新颖见解。我们还确定了候选独立变量，这些变量可以单独或组合使用，以使研究人员能够解释世界事务中非正式治理的增长和分布的显着差异。我们总结了这些贡献的主要发现，并在最后概述了有关世界政治中非正式治理的未来研究议程。