From its first applications to the military domain, HRA progressed to applications in Nuclear Power Plants (NPPs) operations, when development and validation of methods mainly targeted their use in Probabilistic Risk Assessments. In recent years, advances in HRA include the extension to various application fields, the development of new methods or enhancement of existing ones, data collection efforts, among others. These advances are possible due to the increasing number of authors on HRA and collaboration between them. Systematic literature reviews have been increasingly used for understanding various aspects of a research field. While recent reviews have provided an overview of the topics addressed by HRA research, the social structure of the field has not yet been fully explored. This paper discusses the social structure of HRA through 70 years of literature. The review aims at responding to how the links between different authors groups were created, that is, which large-scale projects, geographical proximity, or research topics contributed to these connections. The results indicate that (1) while the research on HRA was mostly based in the U.S.A. before 2000, China, Japan, and South Korea are significant contributors to the recent literature; (2) despite the increasing diversity of application fields, such as applications to the maritime and offshore industry, the main focus on NPPs operations is persistent since the 1980s; (3) due to large research projects, favored by a connected world, the physical workspace does not limit current collaboration among authors.