This document summarizes the evolving landscape of bibliometric data sources and opportunities for bibliometric visualization. It discusses how alternative data sources like Dimensions, Crossref, and OpenCitations Corpus provide more open citation data than traditional sources like Web of Science and Scopus. While coverage varies, Dimensions and Crossref provide reasonably complete publication and citation data. Discrepancies between sources are due to reference inaccuracies and inconsistencies in citation matching. VOSviewer software supports network analysis and visualization using multiple data sources. The document calls for expanding open citation indexing to further open science.

1. Web of Science, Scopus, Dimensions, and beyond:
The evolving landscape of bibliometric data sources
Ludo Waltman, Martijn Visser, Nees Jan van Eck
Centre for Science and Technology Studies (CWTS), Leiden University
ROI-AV Conference: Visuals and Analytics that Matter
Copenhagen, Denmark
October 3, 2018

2. Outline
• Bibliometric data sources
• New opportunities for bibliometric visualization
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3. Bibliometric data
sources
2

4. Introduction
• Increasing number of alternatives (Microsoft Academic, Dimensions,
Crossref, OpenCitations Corpus) to traditional bibliographic data sources
(Web of Science, Scopus, Google Scholar)
• Alternative data sources are more open than traditional ones
• How do the various data sources compare in terms of the completeness and
quality of their citation data?
3

5. 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 2018
– Openly available through API
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6. Coverage of publications
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All publications Publications with DOI
Publications with
unique DOI
Web of Science 40.1 100.0% 18.8 46.9% 18.8 46.9%
Scopus 44.9 100.0% 31.1 69.2% 30.6 68.3%
Dimensions 57.5 100.0% 55.1 95.9% 55.0 95.6%
Crossref 57.3 100.0% 57.3 100.0% 57.3 100.0%
• Publication counts in millions
• Time period 1996-2017

7. Coverage of publications: Dimensions vs. Scopus
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8. Comparison of citation data
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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: 171.3M
Only in Scopus: 292.1M
Only in Crossref: 6.4M
In these pairwise comparisons of data sources, only
citation links between citing and cited publications
indexed in both data sources are considered

9. Causes of discrepancies between data sources
• Inaccuracies in references
• Inaccuracies in reference data
• Inaccuracies in citation matching
• Multiple versions of a publication
• Multiple records for a publication
• References not having been deposited, being closed or not having been
matched
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10. Example: Discrepancies between Scopus and
Dimensions
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11. Example: Discrepancies between Scopus and
Dimensions
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12. Example: Discrepancies between Scopus and Web of
Science
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Group author and/or supplement
seem to cause problems in Web
of Science

13. Example: Discrepancies within Web of Science
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September 20, 2017
November 1, 2017
November 8, 2017

14. Example: Unmatched references in Crossref
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15. Conclusions
• Substantial discrepancies between data sources
• Reasonably complete citation data in Dimensions
• Large gaps in citation data in Crossref, due to references not having been
deposited, being closed or not having been matched
• Need for transparent high-quality citation matching algorithm
• Completeness and quality of other metadata?
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16. New opportunities for
bibliometric
visualization
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17. VOSviewer
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18. Users of VOSviewer
• Researchers
• Research institutions
• Research funders
• Scientific publishers
• Industry
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19. Data sources supported by VOSviewer
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20. Bibliometric networks
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WoS
Scopus
Dimensions
PubMed
Crossref
Citation network
of pubs / journals / authors / orgs / countries
Co-authorship network
of authors / orgs / countries
Co-citation network
of pubs / journals / authors / orgs / countries
Co-occurrence network
of keywords / terms
Bibliographic coupling network
of pubs / journals / authors
Bibliographic
data source

21. Types of networks supported by each data source
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Co-authorship Co-
occurrence
Citation Bibliographic
coupling
Co-citation
Web of Science
    
Scopus
    
Dimensions
    
PubMed
    
Crossref
    

22. Journal citation network based on Crossref data
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23. Demonstration
• Journals:
– Journal of Informetrics (Elsevier)
– Scientometrics (Springer Nature)
• Time period: 2007-2016
• Data sources:
– Dimensions
– Crossref
– OCC (OpenCitations Corpus)
– COCI (OpenCitations Index of Crossref open DOI-to-DOI references)
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24. 23

25. 24

26. 25

27. 26

28. Coverage of publications and citations for each data
source
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29. Wish list for improving open data sources
• Expanding coverage of publications (OCC)
• Opening citations (Crossref)
• Opening other metadata, e.g. abstracts (Dimensions, Crossref, OCC)
• Improving completeness and standardization of metadata (Crossref)
• Speeding up APIs
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30. Toward contextualized scientometrics
• Integrating data collection and visual analysis
• Interactive visual exploration (e.g., drilling down from high-level visual
overviews to underlying data)
• Large-scale visual analyses
• Moving from visualization as a tool for representation to visualization as a
tool for exploration, discussion and reflection
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31. Supporting open
citations
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32. Supporting open citations
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www.issi-society.org/open-citations-letter/
April 26, 2018:
• 324 signatories
• 46 countries

33. Supporting open citations
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www.issi-society.org/blog/posts/2018/april/open-citations-to-open-science/

34. Thank you for your attention!
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