Yesterday (November 23rd 2017) I was working with Daniel Ecer of eLife (firstname.lastname@example.org) to dig some hard facts out of the analyses he undertook on data he downloaded from Crossref in September 2017 (Ecer, 2017). In this, the first of two related posts, I report the results for all publishers.
The analyses show that, of the 33,672,763 journal articles documented in Crossref that have accompanying references, 17,072,801 (50.70%) have open references, and of the 956,050,193 references from journal articles stored at Crossref, 486,041,671 (50.84%) are now classified as “Open”, and are freely available for third parties to download and use for any purpose.
This is a significant milestone for the Initiative for Open Citations (I4OC, https://i4oc.org/), which since early 2017 has been campaigning for scholarly publishers to open their reference lists, and a major gain for the world of open scholarship.
The academic community is deeply indebted to all those publishers whose references are now open (https://i4oc.org/#publishers), and to Crossref itself (https://www.crossref.org/), for making these references freely available, providing a tremendous resource for bibliometric analysis.
However, 51.7% of the journal articles recorded in Crossref lack accompanying references, and of the references that are submitted together with the metadata for the remaining journal articles, 49.16% are yet not open.
On behalf of I4OC, I strongly encourage those publishers who are not yet submitting references to Crossref with their article metadata to start to do so, and those other publishers who are submitting references but have not yet made them open to open them without delay, by sending a message requesting this to email@example.com.
The detailed statistics derived from the Crossref data at the time of sampling relating to all publishers are as follows:
Works with DOIs documented at Crossref
Crossref has records of 93,184,372 works with DOIs, of which 69,699,633 (74.80%) are journal articles and 23,484,739 (25.20%) are works that are not journal articles (i.e. book chapters, proceedings articles, datasets, etc.).
Numbers of works with references
Of all 93,184,372 works with DOIs recorded in Crossref, 38,445,236 (41.3%) have accompanying references and 54,739,136 (58.7%) lack references.
Of the 69,699,633 journal articles recorded in Crossref, 33,672,763 (48.3%) have accompanying references, and 36,026,381 (51.7%) lack references.
Of the 23,484,739 works that are not journal articles recorded in Crossref, 4,772,473 (20.32%) have accompanying references, and 18,709,979 (79.68%) lack references.
Numbers of references at Crossref
Crossref stores 1,075,133,743 references from all 93,184,372 works.
Of these references, 956,050,193 references (88.92%) are from journal articles, and 119,083,550 references (11.08%) are from works that are not journal articles.
Average numbers of references per work
The 1,075,133,743 references stored in Crossref come from 38,445,236 works of all types with accompanying references, giving an average of 27.97 references per work.
956,050,193 references come from 33,672,763 journal articles with accompanying references, giving an average of 28.39 references per journal article.
119,083,550 references come from 4,772,473 works with accompanying references that are not journal articles, averaging 24.95 references per work.
Proportion of works that have open references
Of the 38,445,236 works of all type documented in Crossref that have accompanying references, 18,228,638 (47.41%) have open references.
Of the 33,672,763 journal articles documented in Crossref that have accompanying references, 17,072,801 (50.70%) have open references.
Of the 4,772,473 works documented in Crossref that are not journal articles and that have accompanying references, 1,155,837 (24.22%) have open references.
Proportion of references that are open
Of the 1,075,133,743 references stored in Crossref from works of all types, 523,201,061 (48.66%) are open, and 551,932,682 (51.34%) are not open.
Of the 956,050,193 references stored in Crossref from journal articles, 486,041,671 (50.84%) are open, and 470,008,522 (49.16%) are not open.
Of the 119,083,550 references stored in Crossref from works that are not journal articles, 37,159,390 (31.20%) are open, and 81,924,160 (68.80%) are not open.
The majority of the references that are not yet open are from works published by Elsevier, as detailed in the next post.
[Note: As a result of further calculations undertaken by Daniel Ecer on 27th November 2017, which are recorded in his updated Crossref Data Notebook (Ecer, 2017), the figures in this blog have been expanded to show the average number of references for works submitting references. At the same time, very minor corrections have been made the total numbers of works in each category, which have not altered the percentages and main conclusions presented in this post.]
Ecer, D. (2017). Crossref Data Notebook. Available at https://elifesci.org/crossref-data-notebook