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Total, coverage, and average of references for the overall dataset_
| Indicator | Scholarly references | Policy references |
|---|---|---|
| Total | 23,745,211 | 7,806,381 |
| Coverage | 7.7% | 10.6% |
| Average | 0.17 | 0.14 |
Descriptive statistics of scholarly and policy references in policy documents_
| Indicator | Scholarly references | Policy references |
|---|---|---|
| Minimum | 0 | 0 |
| Maximum | 14,633 | 1,352 |
| 25th percentile | 0 | 0 |
| 50th percentile (median) | 0 | 0 |
| 75th percentile | 0 | 0 |
| 90th percentile | 0 | 1 |
| 99th percentile | 32 | 9 |
| Arithmetic mean | 1.36 | 0.45 |
| Standard deviation | 17.47 | 3.22 |
| Skewness | 154.16 | 46.51 |
| Kurtosis | 67,556.53 | 8,123.57 |
Reference metadata elements from Overton-indexed policy documents_
| Metadata type | Definition |
|---|---|
| Scholarly references | Citations from policy documents to academic literature (i.e., scholarly papers referenced within policy documents). Overton identifies and formats these references by extracting elements from potential reference strings - such as sources, titles, and publication years - from the full text of policy documents, then searching Crossref to retrieve the DOIs of the cited scholarly works (Overton, 2024d, 2024c). |
| Policy references | Citations from one policy documents to another (i.e., policy documents referenced within other policy documents). Overton identifies and formats these references using a method similar to that employed for scholarly references. Policy references are obtained by matching elements of potential reference strings extracted from the full text with indexed policy documents in the Overton database (Overton, 2024d, 2024c). |
Bibliographic metadata elements from Overton-indexed policy documents_
| Metadata type | Definition |
|---|---|
| Publication date | The date when the policy documents were published. |
| Policy source | The organizations or entities from which policy documents are collected. |
| Source type | The categories of policy sources. Overton classifies policy sources into three main types: “government”, “think tank” and “intergovernmental organization (IGO)” (Overton, 2024h). Additionally, Overton tracks policy documents from “other” sources, including open repositories and non-governmental organizations (NGOs). |
| Source country | The countries associated with the policy sources. Notably, IGOs and the European Union (EU) are listed separately. |
| Document language | The languages in which the PDF files of policy documents are written. A single policy document may be released in multiple PDF versions across different languages.① |
| Subject area | The subject areas of policy documents. For documents written in certain languages (e.g., English, French, Spanish), Overton assigns subject areas by matching phrases and entities extracted from the full text with examples from each category in the International Press Telecommunications Council (IPTC)’s Media Topics controlled vocabulary (https://iptc.org/standards/media-topics/)② (Overton, 2024a). |
| Topics | The main themes of policy documents. Overton assigns topics to documents written in certain languages (e.g., English, French, Spanish) by matching phrases and entities extracted from the full text with the titles of Wikipedia pages (Overton, 2024a). |