Differences in citation counts between Scopus and Google Scholar
Anyone who is familiar with Google Scholar (GS) will know that it often provides higher citation counts of articles than Scopus (or other citation databases such as Web of Science). There are many reasons for this, such as including citations that may not be considered scholarly such as PPT presentations, grey literature not indexed by Scopus and because of indexing errors by GS that lead to duplicate citations.
I did a little experiment to see how big a disparity it can be. I used this article as an example: Internet search tactics by Smith, A. G., one of my old lecturers for the MLIS. GS said that it was cited by 7 while Scopus said it was cited by just 1 author. I looked at the extra 6 citations in GS. They included a university thesis, a research article, a dissertation and 3 things in a foreign language: a research article, a citation for something and a link to a Google book. So why hadn't Scopus included these citations? Clearly it doesn't cite sources in another language and it doesn't include citations from Google Books. Another reason may be it does not have the indexing capabilities of GS.
I looked at another example by Smith, A. G., Web based impact measures for institutional repositories. GS says this has been cited by 4 authors while Scopus did not list any. The GS citations included 4 research articles. One had an untrusted connection so I did not access it and another seemed of dubious scholarly worth. Scopus only includes citations from reputable sources so it's no surprise that it hadn't included them.
Here's another article by Smith: Linking to institutional repositories from the general web. Scopus had no citations while GS had 2. One was a self citation and the other was a research project by an author from the same institution as Smith.
Lastly I looked at: Think local, search global? Comparing search engines for searching geographically specific information. There were 5 citations in Scopus and 16 in GS. This time GS included 3 blog posts (definitely not scholarly sources) as well as 2 self citations. Incidentally GS made a parsing error with one of the blog posts - the author is given as "A Sad" which is incorrect.
GS provides higher citation counts because it indexes a wider variety of sources. Scopus only includes citations from journals, academic books and and published academic material such as conference proceedings while GS includes citations from gray literature (e.g. theses in online repositories) and Google Books. GS however also includes self citations and citations from non scholarly sources which need to be eliminated when doing a citation count.
I did a little experiment to see how big a disparity it can be. I used this article as an example: Internet search tactics by Smith, A. G., one of my old lecturers for the MLIS. GS said that it was cited by 7 while Scopus said it was cited by just 1 author. I looked at the extra 6 citations in GS. They included a university thesis, a research article, a dissertation and 3 things in a foreign language: a research article, a citation for something and a link to a Google book. So why hadn't Scopus included these citations? Clearly it doesn't cite sources in another language and it doesn't include citations from Google Books. Another reason may be it does not have the indexing capabilities of GS.
I looked at another example by Smith, A. G., Web based impact measures for institutional repositories. GS says this has been cited by 4 authors while Scopus did not list any. The GS citations included 4 research articles. One had an untrusted connection so I did not access it and another seemed of dubious scholarly worth. Scopus only includes citations from reputable sources so it's no surprise that it hadn't included them.
Here's another article by Smith: Linking to institutional repositories from the general web. Scopus had no citations while GS had 2. One was a self citation and the other was a research project by an author from the same institution as Smith.
Lastly I looked at: Think local, search global? Comparing search engines for searching geographically specific information. There were 5 citations in Scopus and 16 in GS. This time GS included 3 blog posts (definitely not scholarly sources) as well as 2 self citations. Incidentally GS made a parsing error with one of the blog posts - the author is given as "A Sad" which is incorrect.
GS provides higher citation counts because it indexes a wider variety of sources. Scopus only includes citations from journals, academic books and and published academic material such as conference proceedings while GS includes citations from gray literature (e.g. theses in online repositories) and Google Books. GS however also includes self citations and citations from non scholarly sources which need to be eliminated when doing a citation count.
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