The Role of Google Scholar in Evidence Reviews and Its Applicability to Grey Literature Searching
Publication Date
September 17, 2015
Journal
PLOS ONE
Authors
Neal Robert Haddaway, Alexandra Mary Collins, Deborah Coughlin & Stuart Kirk
Volume
10
Issue
9
Pages
e0138237
DOI
https://dx.plos.org/10.1371/journal.pone.0138237
Publisher URL
http://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0138237
PubMed
http://www.ncbi.nlm.nih.gov/pubmed/26379270
PubMed Central
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4574933
Europe PMC
http://europepmc.org/abstract/MED/26379270
Web of Science
000361769400068
Scopus
84945551837
Mendeley
http://www.mendeley.com/research/role-google-scholar-evidence-reviews-applicability-grey-literature-searching
Events
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Mendeley | Further Information

{"title"=>"The role of google scholar in evidence reviews and its applicability to grey literature searching", "type"=>"journal", "authors"=>[{"first_name"=>"Neal Robert", "last_name"=>"Haddaway", "scopus_author_id"=>"54997981700"}, {"first_name"=>"Alexandra Mary", "last_name"=>"Collins", "scopus_author_id"=>"56668291600"}, {"first_name"=>"Deborah", "last_name"=>"Coughlin", "scopus_author_id"=>"56928010800"}, {"first_name"=>"Stuart", "last_name"=>"Kirk", "scopus_author_id"=>"7103258668"}], "year"=>2015, "source"=>"PLoS ONE", "identifiers"=>{"scopus"=>"2-s2.0-84945551837", "sgr"=>"84945551837", "doi"=>"10.1371/journal.pone.0138237", "pui"=>"606624550", "pmid"=>"26379270", "isbn"=>"1932-6203", "issn"=>"19326203"}, "id"=>"dcc2a5b1-289a-3da5-bcb5-7b0efda916e2", "abstract"=>"Google Scholar (GS), a commonly used web-based academic search engine, catalogues between 2 and 100 million records of both academic and grey literature (articles not formally published by commercial academic publishers). Google Scholar collates results from across the internet and is free to use. As a result it has received considerable attention as a method for searching for literature, particularly in searches for grey literature, as required by systematic reviews. The reliance on GS as a standalone resource has been greatly debated, however, and its efficacy in grey literature searching has not yet been investigated. Using systematic review case studies from environmental science, we investigated the utility of GS in systematic reviews and in searches for grey literature. Our findings show that GS results contain moderate amounts of grey literature, with the majority found on average at page 80. We also found that, when searched for specifically, the majority of literature identified using Web of Science was also found using GS. However, our findings showed moderate/poor overlap in results when similar search strings were used in Web of Science and GS (10-67%), and that GS missed some important literature in five of six case studies. Furthermore, a general GS search failed to find any grey literature from a case study that involved manual searching of organisations' websites. If used in systematic reviews for grey literature, we recommend that searches of article titles focus on the first 200 to 300 results. We conclude that whilst Google Scholar can find much grey literature and specific, known studies, it should not be used alone for systematic review searches. Rather, it forms a powerful addition to other traditional search methods. In addition, we advocate the use of tools to transparently document and catalogue GS search results to maintain high levels of transparency and the ability to be updated, critical to systematic reviews.", "link"=>"http://www.mendeley.com/research/role-google-scholar-evidence-reviews-applicability-grey-literature-searching", "reader_count"=>208, "reader_count_by_academic_status"=>{"Unspecified"=>4, "Professor > Associate Professor"=>7, "Librarian"=>38, "Researcher"=>40, "Student > Doctoral Student"=>10, "Student > Ph. D. Student"=>45, "Student > Postgraduate"=>7, "Student > Master"=>21, "Other"=>11, "Student > Bachelor"=>12, "Lecturer"=>5, "Lecturer > Senior Lecturer"=>1, "Professor"=>7}, "reader_count_by_user_role"=>{"Unspecified"=>4, "Professor > Associate Professor"=>7, "Librarian"=>38, "Researcher"=>40, "Student > Doctoral Student"=>10, "Student > Ph. D. Student"=>45, "Student > Postgraduate"=>7, "Student > Master"=>21, "Other"=>11, "Student > Bachelor"=>12, "Lecturer"=>5, "Lecturer > Senior Lecturer"=>1, "Professor"=>7}, "reader_count_by_subject_area"=>{"Unspecified"=>17, "Agricultural and Biological Sciences"=>33, "Arts and Humanities"=>7, "Business, Management and Accounting"=>8, "Computer Science"=>22, "Decision Sciences"=>2, "Earth and Planetary Sciences"=>1, "Economics, Econometrics and Finance"=>5, "Engineering"=>2, "Environmental Science"=>19, "Nursing and Health Professions"=>10, "Biochemistry, Genetics and Molecular Biology"=>1, "Medicine and Dentistry"=>32, "Neuroscience"=>1, "Design"=>1, "Sports and Recreations"=>2, "Pharmacology, Toxicology and Pharmaceutical Science"=>1, "Physics and Astronomy"=>2, "Psychology"=>7, "Social Sciences"=>35}, "reader_count_by_subdiscipline"=>{"Medicine and Dentistry"=>{"Medicine and Dentistry"=>32}, "Social Sciences"=>{"Social Sciences"=>35}, "Decision Sciences"=>{"Decision Sciences"=>2}, "Sports and Recreations"=>{"Sports and Recreations"=>2}, "Physics and Astronomy"=>{"Physics and Astronomy"=>2}, "Psychology"=>{"Psychology"=>7}, "Unspecified"=>{"Unspecified"=>17}, "Environmental Science"=>{"Environmental Science"=>19}, "Pharmacology, Toxicology and Pharmaceutical Science"=>{"Pharmacology, Toxicology and Pharmaceutical Science"=>1}, "Arts and Humanities"=>{"Arts and Humanities"=>7}, "Design"=>{"Design"=>1}, "Engineering"=>{"Engineering"=>2}, "Neuroscience"=>{"Neuroscience"=>1}, "Earth and Planetary Sciences"=>{"Earth and Planetary Sciences"=>1}, "Economics, Econometrics and Finance"=>{"Economics, Econometrics and Finance"=>5}, "Agricultural and Biological Sciences"=>{"Agricultural and Biological Sciences"=>33}, "Computer Science"=>{"Computer Science"=>22}, "Business, Management and Accounting"=>{"Business, Management and Accounting"=>8}, "Nursing and Health Professions"=>{"Nursing and Health Professions"=>10}, "Biochemistry, Genetics and Molecular Biology"=>{"Biochemistry, Genetics and Molecular Biology"=>1}}, "reader_count_by_country"=>{"United States"=>5, "United Kingdom"=>3, "Portugal"=>1, "Spain"=>4, "New Zealand"=>1, "Canada"=>2, "Netherlands"=>1, "Botswana"=>1, "Finland"=>1, "Brazil"=>2, "Denmark"=>1, "Mexico"=>2, "South Africa"=>1, "Slovenia"=>1, "Australia"=>3, "Germany"=>1}, "group_count"=>13}

CrossRef

Scopus | Further Information

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Figshare

  • {"files"=>["https://ndownloader.figshare.com/files/2269582"], "description"=>"<p>Proportion of total a) full text and b) title Google Scholar search results by literature type for 7 case studies (see <a href=\"http://www.plosone.org/article/info:doi/10.1371/journal.pone.0138237#pone.0138237.t002\" target=\"_blank\">Table 2</a> for descriptions of SR codes).</p>", "links"=>[], "tags"=>["article titles focus", "review case studies", "catalogue GS search results", "whilst Google Scholar", "Google scholar", "Google Scholar collates results"], "article_id"=>1547565, "categories"=>["Uncategorised"], "users"=>["Neal Robert Haddaway", "Alexandra Mary Collins", "Deborah Coughlin", "Stuart Kirk"], "doi"=>"https://dx.doi.org/10.1371/journal.pone.0138237.g001", "stats"=>{"downloads"=>3, "page_views"=>17, "likes"=>0}, "figshare_url"=>"https://figshare.com/articles/_Proportion_of_total_a_full_text_and_b_title_Google_Scholar_search_results_by_literature_type_for_7_case_studies_see_Table_2_for_descriptions_of_SR_codes_/1547565", "title"=>"Proportion of total a) full text and b) title Google Scholar search results by literature type for 7 case studies (see Table 2 for descriptions of SR codes).", "pos_in_sequence"=>0, "defined_type"=>1, "published_date"=>"2015-09-17 03:42:42"}
  • {"files"=>["https://ndownloader.figshare.com/files/2269583"], "description"=>"<p>Typical characteristics of academic citation databases and search engines.</p>", "links"=>[], "tags"=>["article titles focus", "review case studies", "catalogue GS search results", "whilst Google Scholar", "Google scholar", "Google Scholar collates results"], "article_id"=>1547566, "categories"=>["Uncategorised"], "users"=>["Neal Robert Haddaway", "Alexandra Mary Collins", "Deborah Coughlin", "Stuart Kirk"], "doi"=>"https://dx.doi.org/10.1371/journal.pone.0138237.t001", "stats"=>{"downloads"=>3, "page_views"=>5, "likes"=>0}, "figshare_url"=>"https://figshare.com/articles/_Typical_characteristics_of_academic_citation_databases_and_search_engines_/1547566", "title"=>"Typical characteristics of academic citation databases and search engines.", "pos_in_sequence"=>0, "defined_type"=>3, "published_date"=>"2015-09-17 03:42:42"}
  • {"files"=>["https://ndownloader.figshare.com/files/2269584"], "description"=>"<p>Searches were performed on 06/02/15. Web of Science includes the following databases as part of the MISTRA EviEM subscription; KCI-Korean Journal Database, SciELO Citation Index and Web of Sciences Core Collection.</p>", "links"=>[], "tags"=>["article titles focus", "review case studies", "catalogue GS search results", "whilst Google Scholar", "Google scholar", "Google Scholar collates results"], "article_id"=>1547567, "categories"=>["Uncategorised"], "users"=>["Neal Robert Haddaway", "Alexandra Mary Collins", "Deborah Coughlin", "Stuart Kirk"], "doi"=>"https://dx.doi.org/10.1371/journal.pone.0138237.t002", "stats"=>{"downloads"=>1, "page_views"=>12, "likes"=>0}, "figshare_url"=>"https://figshare.com/articles/_Systematic_reviews_SRs_used_as_case_studies_and_their_search_strings_along_with_modifications_to_WoS_search_strings_necessary_to_function_in_Google_Scholar_advanced_search_facility_as_indicated_by_strikethrough_text_/1547567", "title"=>"Systematic reviews (SRs) used as case studies and their search strings (along with modifications to WoS search strings necessary to function in Google Scholar advanced search facility as indicated by strikethrough text).", "pos_in_sequence"=>0, "defined_type"=>3, "published_date"=>"2015-09-17 03:42:42"}
  • {"files"=>["https://ndownloader.figshare.com/files/2269585"], "description"=>"<p>See <a href=\"http://www.plosone.org/article/info:doi/10.1371/journal.pone.0138237#pone.0138237.t002\" target=\"_blank\">Table 2</a> for case study explanations.</p>", "links"=>[], "tags"=>["article titles focus", "review case studies", "catalogue GS search results", "whilst Google Scholar", "Google scholar", "Google Scholar collates results"], "article_id"=>1547568, "categories"=>["Uncategorised"], "users"=>["Neal Robert Haddaway", "Alexandra Mary Collins", "Deborah Coughlin", "Stuart Kirk"], "doi"=>"https://dx.doi.org/10.1371/journal.pone.0138237.t003", "stats"=>{"downloads"=>1, "page_views"=>20, "likes"=>0}, "figshare_url"=>"https://figshare.com/articles/_Overlap_between_Web_of_Science_WoS_and_Google_Scholar_GS_for_title_searches_in_Web_of_Science_and_the_first_1_000_search_results_from_title_searches_in_Google_Scholar_/1547568", "title"=>"Overlap between Web of Science (WoS) and Google Scholar (GS) for title searches in Web of Science and the first 1,000 search results from title searches in Google Scholar.", "pos_in_sequence"=>0, "defined_type"=>3, "published_date"=>"2015-09-17 03:42:42"}
  • {"files"=>["https://ndownloader.figshare.com/files/2269586"], "description"=>"<p>n/a corresponds to search results that were too voluminous to download in full. See <a href=\"http://www.plosone.org/article/info:doi/10.1371/journal.pone.0138237#pone.0138237.t002\" target=\"_blank\">Table 2</a> for case study explanations.</p>", "links"=>[], "tags"=>["article titles focus", "review case studies", "catalogue GS search results", "whilst Google Scholar", "Google scholar", "Google Scholar collates results"], "article_id"=>1547569, "categories"=>["Uncategorised"], "users"=>["Neal Robert Haddaway", "Alexandra Mary Collins", "Deborah Coughlin", "Stuart Kirk"], "doi"=>"https://dx.doi.org/10.1371/journal.pone.0138237.t004", "stats"=>{"downloads"=>1, "page_views"=>15, "likes"=>0}, "figshare_url"=>"https://figshare.com/articles/_Overlap_between_Web_of_Science_WoS_and_Google_Scholar_GS_for_topic_word_searches_in_Web_of_Science_and_the_first_1_000_search_results_from_full_text_searches_in_Google_Scholar_/1547569", "title"=>"Overlap between Web of Science (WoS) and Google Scholar (GS) for topic word searches in Web of Science and the first 1,000 search results from full text searches in Google Scholar.", "pos_in_sequence"=>0, "defined_type"=>3, "published_date"=>"2015-09-17 03:42:42"}
  • {"files"=>["https://ndownloader.figshare.com/files/2269587"], "description"=>"<p>Numbers in parentheses correspond to the standard deviations of the individual case study duplication rates. Sample size refers to the number of search records in total, followed by the number of independent search strings (i.e. the number of case studies investigated).</p>", "links"=>[], "tags"=>["article titles focus", "review case studies", "catalogue GS search results", "whilst Google Scholar", "Google scholar", "Google Scholar collates results"], "article_id"=>1547570, "categories"=>["Uncategorised"], "users"=>["Neal Robert Haddaway", "Alexandra Mary Collins", "Deborah Coughlin", "Stuart Kirk"], "doi"=>"https://dx.doi.org/10.1371/journal.pone.0138237.t005", "stats"=>{"downloads"=>1, "page_views"=>7, "likes"=>0}, "figshare_url"=>"https://figshare.com/articles/_Duplication_rates_proportion_of_total_results_that_are_duplicates_for_Google_Scholar_and_Web_of_Science_for_title_level_topic_word_and_full_text_searches_using_7_case_study_systematic_review_search_strings_/1547570", "title"=>"Duplication rates (proportion of total results that are duplicates) for Google Scholar and Web of Science for title-level, topic word and full text searches using 7 case study systematic review search strings.", "pos_in_sequence"=>0, "defined_type"=>3, "published_date"=>"2015-09-17 03:42:42"}
  • {"files"=>["https://ndownloader.figshare.com/files/2269588"], "description"=>"<p>Duplication rates are assessed for up to 1,000 search records (or the total number where less than c. 1,300). For Web of Science the full text results were ordered by publication date (newest first) and relevance where more than 1,000 results were returned. Numbers are duplication rate (%) followed by total search records in parentheses.</p>", "links"=>[], "tags"=>["article titles focus", "review case studies", "catalogue GS search results", "whilst Google Scholar", "Google scholar", "Google Scholar collates results"], "article_id"=>1547571, "categories"=>["Uncategorised"], "users"=>["Neal Robert Haddaway", "Alexandra Mary Collins", "Deborah Coughlin", "Stuart Kirk"], "doi"=>"https://dx.doi.org/10.1371/journal.pone.0138237.t006", "stats"=>{"downloads"=>7, "page_views"=>15, "likes"=>0}, "figshare_url"=>"https://figshare.com/articles/_Duplication_rates_proportion_of_total_results_that_are_duplicates_in_Google_Scholar_and_Web_of_Science_searches_across_the_7_case_studies_/1547571", "title"=>"Duplication rates (proportion of total results that are duplicates) in Google Scholar and Web of Science searches across the 7 case studies.", "pos_in_sequence"=>0, "defined_type"=>3, "published_date"=>"2015-09-17 03:42:42"}
  • {"files"=>["https://ndownloader.figshare.com/files/2269590"], "description"=>"<p><sup>1</sup> For those articles not found using Google Scholar, Web of Science searches were carried out using Bangor University subscription (Biological Abstracts, MEDLINE, SciELO Citation Index, Web of Science Core Collections, Zoological Record).</p><p>Records identified as citations are found only within reference lists of other articles (their existence is not verified by the presence of a publisher version or full text article, unlike hyperlinked citations).</p>", "links"=>[], "tags"=>["article titles focus", "review case studies", "catalogue GS search results", "whilst Google Scholar", "Google scholar", "Google Scholar collates results"], "article_id"=>1547573, "categories"=>["Uncategorised"], "users"=>["Neal Robert Haddaway", "Alexandra Mary Collins", "Deborah Coughlin", "Stuart Kirk"], "doi"=>"https://dx.doi.org/10.1371/journal.pone.0138237.t007", "stats"=>{"downloads"=>2, "page_views"=>16, "likes"=>0}, "figshare_url"=>"https://figshare.com/articles/_The_ability_of_Google_Scholar_to_find_included_articles_from_six_published_systematic_reviews_/1547573", "title"=>"The ability of Google Scholar to find included articles from six published systematic reviews.", "pos_in_sequence"=>0, "defined_type"=>3, "published_date"=>"2015-09-17 03:42:42"}
  • {"files"=>["https://ndownloader.figshare.com/files/2269595", "https://ndownloader.figshare.com/files/2269596", "https://ndownloader.figshare.com/files/2269597"], "description"=>"<div><p>Google Scholar (GS), a commonly used web-based academic search engine, catalogues between 2 and 100 million records of both academic and grey literature (articles not formally published by commercial academic publishers). Google Scholar collates results from across the internet and is free to use. As a result it has received considerable attention as a method for searching for literature, particularly in searches for grey literature, as required by systematic reviews. The reliance on GS as a standalone resource has been greatly debated, however, and its efficacy in grey literature searching has not yet been investigated. Using systematic review case studies from environmental science, we investigated the utility of GS in systematic reviews and in searches for grey literature. Our findings show that GS results contain moderate amounts of grey literature, with the majority found on average at page 80. We also found that, when searched for specifically, the majority of literature identified using Web of Science was also found using GS. However, our findings showed moderate/poor overlap in results when similar search strings were used in Web of Science and GS (10–67%), and that GS missed some important literature in five of six case studies. Furthermore, a general GS search failed to find any grey literature from a case study that involved manual searching of organisations’ websites. If used in systematic reviews for grey literature, we recommend that searches of article titles focus on the first 200 to 300 results. We conclude that whilst Google Scholar can find much grey literature and specific, known studies, it should not be used alone for systematic review searches. Rather, it forms a powerful addition to other traditional search methods. In addition, we advocate the use of tools to transparently document and catalogue GS search results to maintain high levels of transparency and the ability to be updated, critical to systematic reviews.</p></div>", "links"=>[], "tags"=>["article titles focus", "review case studies", "catalogue GS search results", "whilst Google Scholar", "Google scholar", "Google Scholar collates results"], "article_id"=>1547576, "categories"=>["Uncategorised"], "users"=>["Neal Robert Haddaway", "Alexandra Mary Collins", "Deborah Coughlin", "Stuart Kirk"], "doi"=>["https://dx.doi.org/10.1371/journal.pone.0138237.s001", "https://dx.doi.org/10.1371/journal.pone.0138237.s002", "https://dx.doi.org/10.1371/journal.pone.0138237.s003"], "stats"=>{"downloads"=>2, "page_views"=>5, "likes"=>0}, "figshare_url"=>"https://figshare.com/articles/_The_Role_of_Google_Scholar_in_Evidence_Reviews_and_Its_Applicability_to_Grey_Literature_Searching_/1547576", "title"=>"The Role of Google Scholar in Evidence Reviews and Its Applicability to Grey Literature Searching", "pos_in_sequence"=>0, "defined_type"=>4, "published_date"=>"2015-09-17 03:42:42"}

PMC Usage Stats | Further Information

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  • {"unique-ip"=>"82", "full-text"=>"97", "pdf"=>"8", "scanned-summary"=>"0", "scanned-page-browse"=>"0", "figure"=>"0", "supp-data"=>"0", "cited-by"=>"0", "year"=>"2018", "month"=>"10"}
  • {"unique-ip"=>"68", "full-text"=>"74", "pdf"=>"2", "scanned-summary"=>"0", "scanned-page-browse"=>"0", "figure"=>"0", "supp-data"=>"0", "cited-by"=>"0", "year"=>"2018", "month"=>"12"}
  • {"unique-ip"=>"97", "full-text"=>"102", "pdf"=>"16", "scanned-summary"=>"0", "scanned-page-browse"=>"0", "figure"=>"0", "supp-data"=>"1", "cited-by"=>"1", "year"=>"2018", "month"=>"11"}
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  • {"unique-ip"=>"209", "full-text"=>"229", "pdf"=>"24", "scanned-summary"=>"0", "scanned-page-browse"=>"0", "figure"=>"0", "supp-data"=>"1", "cited-by"=>"0", "year"=>"2019", "month"=>"3"}
  • {"unique-ip"=>"198", "full-text"=>"222", "pdf"=>"20", "scanned-summary"=>"0", "scanned-page-browse"=>"0", "figure"=>"0", "supp-data"=>"3", "cited-by"=>"0", "year"=>"2019", "month"=>"4"}
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  • {"unique-ip"=>"156", "full-text"=>"174", "pdf"=>"16", "scanned-summary"=>"0", "scanned-page-browse"=>"0", "figure"=>"0", "supp-data"=>"0", "cited-by"=>"0", "year"=>"2019", "month"=>"8"}
  • {"unique-ip"=>"225", "full-text"=>"270", "pdf"=>"13", "scanned-summary"=>"0", "scanned-page-browse"=>"0", "figure"=>"0", "supp-data"=>"1", "cited-by"=>"1", "year"=>"2019", "month"=>"9"}
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  • {"unique-ip"=>"399", "full-text"=>"488", "pdf"=>"39", "scanned-summary"=>"0", "scanned-page-browse"=>"0", "figure"=>"0", "supp-data"=>"0", "cited-by"=>"4", "year"=>"2020", "month"=>"3"}
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Relative Metric

{"start_date"=>"2015-01-01T00:00:00Z", "end_date"=>"2015-12-31T00:00:00Z", "subject_areas"=>[]}
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