Overton, a global policy index, provides new opportunities to study the interactions between science and policy. This study aims to characterize the presence of scholarly and policy references in Overton-indexed policy documents and examine their distribution across key bibliographic dimensions, thereby assessing Overton's potential as a data source for policy metrics. We analyze a dataset of approximately 17.5 million policy documents from Overton, incorporating metadata such as publication year, policy source, country, language, subject area, and policy topic. Descriptive statistics are employed to assess the presence and distribution of reference data across these dimensions. Overton indexes a substantial volume of policy documents and identifies considerable reference data within them: 7.7% of documents contain scholarly references and 10.6% contain policy references. However, the presence of references varies significantly across publications years, source types, countries, languages, subject areas, and policy topics, indicating coverage biases that may affect interpretations of policy impact. The analysis is based on the Overton database as of June 2025. As Overton is regularly updated, the distribution patterns of indexed documents and references may evolve over time. The findings offer insights into the opportunities and constraints of using Overton for investigating evidence-based policymaking and for assessing the policy uptake of research outputs in the context of research evaluation. This is the first large-scale study to systematically examine the distribution of reference data in Overton. It contributes a foundational understanding of this emerging source for policy metrics, highlighting both its potential applications and limitations, and underlining the importance of addressing current coverage imbalances.

翻译：全球政策索引数据库Overton为研究科学与政策互动提供了新的机遇。本研究旨在刻画Overton索引政策文件中学术参考文献与政策参考文献的存在特征，并考察其在关键文献计量维度上的分布规律，从而评估Overton作为政策计量数据源的潜力。我们分析了Overton中约1750万份政策文档数据集，整合了出版年份、政策来源、国家、语言、学科领域和政策议题等元数据。采用描述性统计方法评估参考文献数据在这些维度上的存在情况与分布特征。Overton收录了海量政策文献并识别出其中大量参考文献数据：7.7%的文档包含学术参考文献，10.6%包含政策参考文献。然而，参考文献的存在比例在出版年份、来源类型、国家、语言、学科领域和政策议题等维度上呈现显著差异，表明数据库存在可能影响政策影响力解读的覆盖偏差。本分析基于截至2025年6月的Overton数据库。由于Overton定期更新，索引文档与参考文献的分布模式可能随时间演变。研究结果为利用Overton探究循证决策机制、评估研究成果在政策实践中的转化应用提供了机遇与局限性的双重启示。这是首个系统考察Overton参考文献数据分布的大规模研究，为这一新兴政策计量数据源奠定了基础认知，既揭示了其潜在应用价值，也指明了现有局限，并强调了解决当前覆盖不均衡问题的重要性。