1. Crossref as a source of open bibliographic
metadata
Nees Jan van Eck and Ludo Waltman
Centre for Science and Technology Studies (CWTS), Leiden University
18th International Conference on Scientometrics & Informetrics
Leuven, Belgium, July 12-15, 2021

2. Introduction
• Crossref is becoming an increasingly interesting data
source for bibliometric analyses
• Several initiatives have been taken to promote the open
availability of bibliographic metadata of scholarly
publications in Crossref:
– Initiative for Open Citations (launched in 2017)
– Initiative for Open Abstracts (launched in 2020)
• There are still many publications in Crossref for which
important metadata elements are missing
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3. Aim
• We present an up-to-date overview of the availability of bibliographic
metadata in Crossref, focusing on six metadata elements:
– reference lists
– abstracts
– ORCIDs
– author affiliations
– funding information
– license information
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4. Data
• Crossref’s XML Metadata Plus Snapshot
(downloaded on March 5, 2021)
• 86.4 million records classified as
journal article:
– 2000-2020: 52.8 million journal articles
– 2019-2020: 8.8 million journal articles
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5. Yearly number of journal articles
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6. Increasing availability of metadata over time
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7. Publisher analysis (2019-2020)
• For the 8.8 million journal articles in Crossref in 2019 and 2020, we
determined for each publisher the percentage of articles that have:
• an openly available reference list
• an abstract
• at least one ORCID
• at least one author affiliation
• funding information
• license information
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8. Publisher analysis (2019-2020): References
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9. Publisher analysis (2019-2020): Abstracts
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10. Publisher analysis (2019-2020): ORCIDs
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11. Publisher analysis (2019-2020): Affiliations
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12. Publisher analysis (2019-2020): Funding information
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13. Publisher analysis (2019-2020): License information
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14. Visualizing a journal citation network
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86.4 million journal articles
1.32 billion references
0.94 billion citation links with
other journal articles
Interactive version: https://bit.ly/3dNHA2A

15. Conclusions
• Open bibliographic metadata helps:
– to make bibliometric analyses more transparent, reproducible, and inclusive
– to make it easier to find the most relevant scholarly literature
• Open availability of different metadata elements in Crossref has
improved over time
• Many publishers need to make additional efforts to realize full
openness of bibliographic metadata:
– publishers often do a good job in making certain metadata elements openly
available, but they fail to do the same for other metadata elements
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16. Future research
• Calculate more detailed statistics
• Examine other content types:
– conference papers
– book chapters
– preprints
– data sets
– peer review reports
• Analyze links between journal articles and other content types
(e.g., preprints, data sets, peer review reports)
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17. ecknjpvan@cwts.leidenuniv.nl
@neesjanvaneck
www.cwts.nl/people/neesjanvaneck
Thank you
for your attention!