In 2004, Elsevier launched Scopus as a new search and discovery tool . Scopus is an abstract and citation database consisting of peer-reviewed scientific content. At its launch, it contained about 27 million publication records (1966–2004). Since then, the content of the database has grown to over 76 million records at the time of writing, covering publications from 1788–2019, making it among the largest curated bibliographic abstract and citation databases today. Approximately 3 million new items are being added every year. The content in Scopus is sourced from over 39,100 serial titles (with the most recently published content indexed from over 24,500 titles), 120,000 conferences, and 206,000 books from over 5,000 different publishers worldwide. Scopus is a curated database, which means that content is selected for inclusion in the database through a rigorous process: Serial content (i.e., journals, conference proceedings, and book series) submitted for possible inclusion in Scopus by editors and publishers is reviewed and selected, based on criteria of scientific quality and rigor. This selection process is carried out by an external Content Selection and Advisory Board (CSAB) of editorially independent scientists, each of which are subject matter experts in their respective fields. This ensures that only high-quality curated content is indexed in the database and affirms the trustworthiness of Scopus. In addition, Scopus being a curated database also refers to the rigorous capturing procedures, publisher agreements, and technical infrastructure in place to source the publications directly from the publishers themselves, ensuring comprehensive, complete, and accurate coverage of the serial content once it has been selected by the CSAB.
Scopus indexes many different elements of scientific publications, obtained from external publishers, such as publication title, abstract, keywords, author names and linked affiliations, references, and drug terms . Content in Scopus contains publications from scientific publishers from all over the world. Elsevier, the owner of Scopus, is also a scientific publisher. About 9.9% of the serial titles (i.e., journals and book series) in Scopus are published by Elsevier (this amounts to an article share in Scopus of 17.4% between 2012 and 2018); the other 90.1% of serial titles (and 82.6% of articles, respectively) are produced by an extensive list of global publishers. In addition, subject coverage of the serial titles in Scopus is quite balanced among the four main subject categories. Scopus also includes non-English content, as long as an English title and abstract, as well as references in Roman script, are available.
A substantial number of author profiles in Scopus have been curated. Curation can be initiated through a variety of sources. A well-established process is through Open Researcher and Contributor ID (ORCID), an open, non-proprietary registry of unique, persistent author identification codes . ORCID is managed by a non-profit organization with the same name established in 2012. Researchers can export, import, or link their publications and curated metadata between Scopus and ORCID. Similarly, researchers can use a feature on Scopus.com called the “Author Feedback Wizard” (AFW) to improve their author profile. Finally, yet another process that results in improved, curated Scopus author profiles is a commercial service offered by Elsevier to subscribers of its “Pure” university administration product, called Profile Refinement Service. Pure customers can opt to have their profiles refined upon request or refined every 4 months. Elsevier uses the same service to proactively refine author profiles regardless of Pure subscription whenever needed.
All above efforts combined have led to approximately 1.8 million Scopus author profiles that have been manually enhanced (Scopus index, July 2019). This total has been verified using a “manual curated” flag in the XML data of Scopus author profile records. Nonetheless, we must emphasize that Scopus creates author profiles that are being actively updated by algorithms for all authorships (of over 76 million publications) covered. Availability of author profiles throughout the corpus enables author level analytics and benchmarking across the database beyond subsample estimations. Moreover, Scopus author profiles are designed to be a complete publication history and so will not remove or hide select publications for personal gain (i.e., negatively impacting publications, such as retraction notices, errata, suspiciously funded). In fact, feedback that Elsevier receives is algorithmically and manually reviewed before changing any existing profile.
An important aspect of the Scopus database is the high coverage and availability of first names, even for relatively old records: from 25% of authorships in 1970–1974 and 52% between 1995–1999 to 82% of authorships in 2015–2019 . This feature strengthens the disambiguation of authors and allows, for instance, gender-based longitudinal analyses that leverage first names (Elsevier, 2017; Lerchenmueller & Sorenson, 2018). Another relevant aspect in the analytical context is the availability of author-affiliation links in publications throughout the database historically. This enables studies dealing with the mobility of researchers, by analyzing the author affiliations and how they change over time.
An important enrichment in the Scopus database is that of institution profiles, allowing different name variants and hierarchies of institutions to be curated in a similar fashion as authors, thereby allowing automated organizing of information where needed (via an advanced, proprietary, and highly accurate institutional profiling algorithm) and manual modification and instruction, where possible. In addition, the full text of articles sourced by Scopus is processed using natural language processing to identify potential references to funding acknowledgements.
To maintain Scopus as a high-quality data source and push the boundaries of quality forward, Scopus introduced internal review processes to constantly monitor preidentified areas of quality focus, such as processing, profile quality, and completeness and accuracy of source data. This allows the content team to identify early trends in the data and to monitor progress on key initiatives to increase quality. For instance, under this program, digital object identifier (DOI) completion rates went up from 87.8% at the start of the program to 99.8% in December 2018. The completeness was measured across a gold record set for which each should have a DOI. Other main focus areas where significant improvements have been made over the past few years, and where continuous investments are being made, are completeness of indexed publication records for the serial titles covered (by weekly comparisons against the CrossRef database), the removal of duplicate MedLine and Article in Press records, the correctness and completeness of citation links (by measuring against a gold set), of the author and institution profiles and publication record metadata (such as document type classifications, publication years, article numbers, country codes, and funding information), as well as improving the timeliness and currency of newly indexed content. These quality review processes employ machine learning approaches, supplemented with manual validation, and concern legacy content (i.e., content already indexed in Scopus) as well as continuously improving and fine-tuning the capturing procedures for newly indexed content.
In addition to expanding and enriching the content, as well as improving the timeliness of the database, a curated database such as Scopus requires re-evaluation of the appropriateness of new and already indexed titles on an ongoing basis. This is needed to exclude poor-quality journals and “predatory” journals and publishers, a relatively recent phenomenon that is a threat to the integrity of science, as well as an increasing challenge to all research publishing stakeholders: authors, editors, researchers, research institutions, funding bodies, research assessment bodies, and governments. To ensure that only the most reliable scientific articles and content are available in Scopus to each of these stakeholders and that the quality of the existing content is maintained, a rigorous process of continuous monitoring and re-evaluation has been installed. This means that titles that have been selected for inclusion in Scopus may be discontinued and no longer indexed going forward. There are three different identification techniques applied, using (a) external feedback (i.e., formally raised concerns about publication standards), (b) heuristics (metrics) to flag underperforming journals, and (c) a machine learning approach to flag outlier behavior, which each lead to titles being tagged for re-evaluation. The ultimate decision to (de)select content lies with the external and independent Scopus CSAB (for full details, please see Elsevier, 2019b; Holland, Brimblecombe, Meester, & Steiginga, 2019). For publications of which the CSAB determines they no longer meet the quality standards for inclusion in Scopus, indexing of new content is discontinued, but content already indexed remains in Scopus, to ensure the integrity of the scientific record as well the stability and consistency of research trend analytics.