Google Scholar, Web of Science, and Scopus: a systematic comparison of citations in 252 subject categories

By Alberto Mart'in-Mart'in, Enrique Orduña-Malea, Mike Thelwall, Emilio Delgado López-Cózar. J. Informetrics, 2018

1,745 citations recorded by the source corpus.

Despite citation counts from Google Scholar (GS), Web of Science (WoS), and Scopus being widely consulted by researchers and sometimes used in research evaluations, there is no recent or systematic evidence about the differences between them. In response, this paper investigates 2,448,055 citations to 2,299 English-language highly-cited documents from 252 GS subject categories published in 2006, comparing GS, the WoS Core Collection, and Scopus. GS consistently found the largest percentage of citations across all areas (93%-96%), far ahead of Scopus (35%-77%) and WoS (27%-73%). GS found nearly all the WoS (95%) and Scopus (92%) citations. Most citations found only by GS were from non-journal sources (48%-65%), including theses, books, conference papers, and unpublished materials. Many were non-English (19%-38%), and they tended to be much less cited than citing sources that were also in Scopus or WoS. Despite the many unique GS citing sources, Spearman correlations between citation counts in GS and WoS or Scopus are high (0.78-0.99). They are lower in the Humanities, and lower between GS and WoS than between GS and Scopus. The results suggest that in all areas GS citation data is essentially a superset of WoS and Scopus, with substantial extra coverage.

Subfields: Information Systems, Information Systems and Management, Statistics and Probability

View Paper: https://www.semanticscholar.org/paper/e48055e54b6c80661d59b6cba16115661e4d3377

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Citations in the corpus

NRC Publications Archive Archives des publications du CNRC (neutral): “This is also how past work has studied Google Scholar (Khabsa and Giles, 2014; Ordu˜na-Malea et al., 2014; Mart´ın-Mart´ın et al., 2018).”
Google Scholar, Microsoft Academic, Scopus, Dimensions, Web of Science, and OpenCitations’ COCI: a multidisciplinary comparison of coverage via citations (2020, methodology): “Instead, a custom web scraper was used to extract the list of citing documents for each highly-cited document in the seed sample (Martín-Martín 2018).”
Examining Citations of Natural Language Processing Literature (2020, background): “This is also how past work has studied Google Scholar (Khabsa and Giles, 2014; Ordu˜na-Malea et al., 2014; Mart´ın-Mart´ın et al., 2018).”
Web of Science (WoS) and Scopus: The Titans of Bibliographic Information in Today's Academic World (2021, background): “These results were confirmed by later comparisons that were performed at the publication level, showing that both DBs offer the widest coverage of Natural, Medicine, Health Sciences, and Technology, while Social Sciences and Humanities (SSH) are underrepresented in both DBs [40,49,53,56].”