Crossref as a new source of citation data: A comparison with Web of Science and Scopus
ab1630's bookmarks 2018-03-28
"The Initiative for Open Citations (I4OC) encourages scholarly publishers to make the references found in their journals and books openly available through Crossref. With a few exceptions (most notably the American Chemical Society, Elsevier, IEEE, and Wolters Kluwer Health), almost all large publishers support the initiative. So far, this support has resulted in approximately half of all references deposited in Crossref being openly available, yielding about half a billion open references. I4OC has attracted widespread attention. The initiative is of particular importance for the scientometric community. Thanks to I4OC, Crossref has the potential to become an openly available source of citation data covering a large share of all scholarly literature. I4OC has been endorsed by CWTS and the International Society for Scientometrics and Informetrics. Last month, an open letter from the scientometric community was published calling for publishers to open their references. This letter has already been signed by nearly 300 individuals. At present, scientometricians typically obtain citation data from Web of Science (WoS) and Scopus, two proprietary data sources. In this post, we provide empirical insights into the value of Crossref as a new source of citation data. We compare Crossref with WoS and Scopus, focusing on the citation data that is available in the different data sources. Our analysis will show that more than three-quarters of the references in WoS and more than two-thirds of the Scopus references can be found in Crossref, with about half of these references being openly available. On the other hand, it will also be shown that millions of references are missing in Crossref. These references occur in publications that have been deposited in Crossref without their references. The statistics presented in this post are based on WoS and Scopus data provided to CWTS in September 2017 and May 2017, respectively. The Crossref data was downloaded through the Crossref API in August 2017. For WoS, we consider the Science Citation Index Expanded, the Social Sciences Citation Index, the Arts & Humanities Citation Index, and the Conference Proceedings Citation Index. Other citation indices included in WoS, in particular the Emerging Sources Citation Index and the Book Citation Index, are not taken into account, as we do not have access to them...."