Scott L.
Hooper
Ohio University, Athens, USA
Nature 483, 36 (01 March 2012)
doi:10.1038/483036c |
Carles
Alcaraz & Sofia Morais
Institute of Agrifood Research and Technology (IRTA), Sant
Carles de la Rąpita, Spain
Nature 483, 36 (01 March 2012)
doi:10.1038/483036d |
Citations: not all
measures are equal
The scientific community needs to be aware of the limitations of Google
Scholar's personalized citation reports. Clicking on 'My citations' on
the site may offer a nice ego boost, but I would not recommend using the
reports for decisions that could affect careers.
Google Scholar overestimates the number of citable articles (in
comparison with formal citation services such as Scopus and Thomson
Reuters) because of the automated way it collects data, including 'grey'
literature such as theses. For my own publications, for example, Google
Scholar yields 38% more citations and boosts the h-index by 26%.
A citation report for one of my articles revealed that Google Scholar
had counted as independent citations four web pages on which authors had
posted copies of their articles, plus one listing only an article title;
and one to a paper in which my name didn't appear. Personalized searches
by my colleagues exposed comparable errors.
These drawbacks might also allow unscrupulous individuals to use such
tactics to inflate their citation reports, particularly as independent
vetting is blocked by password access.
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Citations: results
differ by database
Databases such as Thomson Reuters' ISI Web of Science, Scopus,
Google Scholar and Microsoft's Academic Search allow authors to compute
their own citation statistics, but they yield inconsistent results.
The discrepancies come from differences in information sources and in
temporal citation coverage. Web of Science and Scopus, for example,
provide citation data only for their indexed journals, giving different
coverage for the number of journals, precursor articles and fields of
academic research often with regional biases (such as European versus
US sources). Google Scholar includes all journals (indexed, free access
and popular science), conference proceedings, books, theses, reports,
local press and electronic sources all subject to variable degrees of
control and scrutiny.
A debate is crucial on how these tracking tools compare and should be
used, given that their indiscriminate usage has potentially negative
implications for academic careers.
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