Comparing bibliographic data sources

Comparing bibliographic data sources

• 1.
  Comparing bibliographic datasources Ludo Waltman, Martijn Visser, Nees Jan van Eck Centre for Science and Technology Studies (CWTS), Leiden University Workshop on Open Citations Bologna September 3, 2018
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  Introduction • Increasing numberof alternatives (Google Scholar, Microsoft Academic, Dimensions, Crossref, OpenCitations Corpus) to traditional bibliographic data sources (Web of Science, Scopus) • Some alternatives are more open than others • How do the various data sources compare in terms of the completeness and quality of their citation data? 1
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  Data sources • Scopus –May 2018 – Requires subscription • Web of Science – SCIE, SSCI, AHCI, CPCI – June 2018 – Requires subscription • Dimensions – June 2018 – Openly available through web interface • Crossref – August 2017 – Openly available through API 2
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  Coverage of publications 3 Allpublications Publications with DOI Publications with unique DOI Web of Science 40.06 100.0% 18.79 46.9% 18.77 46.9% Scopus 44.88 100.0% 31.06 69.2% 30.64 68.3% Dimensions 57.47 100.0% 55.09 95.9% 54.95 95.6% Crossref 53.81 100.0% 53.81 100.0% 53.81 100.0% • Publication counts in millions • Time period 1996-2017 • Note that Crossref is incomplete in 2017
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  Coverage of publications:Dimensions vs. Scopus 4
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  Comparison of citationdata 5 Scopus-WoS overlap: 460.0M Only in Scopus: 24.9M Only in WoS: 15.5M Scopus-Dimensions overlap: 414.3M Only in Scopus: 43.5M Only in Dimensions: 17.9M Scopus-Crossref overlap: 144.1M Only in Scopus: 305.1M Only in Crossref: 5.4M In these pairwise comparisons of data sources, only citation links between citing and cited publications indexed in both data sources are considered
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  Causes of discrepanciesbetween data sources • Inaccuracies in references • Inaccuracies in reference data • Inaccuracies in citation matching • Multiple versions of a publication • Multiple records for a publication • Citations being closed or not having been deposited 6
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  Example: Discrepancies betweenScopus and Dimensions 7
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  Example: Discrepancies betweenScopus and Dimensions 8
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  Example: Discrepancies betweenScopus and Web of Science 9 Group author and/or supplement seem to cause problems in Web of Science
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  Example: Discrepancies withinWeb of Science 10 September 20, 2017 November 1, 2017 November 8, 2017
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  Conclusions • Substantial discrepanciesbetween data sources • Reasonably complete citation data in Dimensions • Large gaps in citation data in Crossref, due to citations being closed or not having been deposited • Need for transparent high-quality citation matching algorithm • Completeness and quality of other metadata? 11
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  Thank you foryour attention! 12