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Google Scholar as replacement for systematic literature searches: good relative recall and precision are not enough
Open accessAbstract
BACKGROUND: Recent research indicates a high recall in Google Scholar searches for systematic reviews. These reports raised high expectations of Google Scholar as a unified and easy to use search interface. However, studies on the coverage of Google Scholar rarely used the search interface in a realistic approach but instead merely checked for the existence of gold standard references. In addition, the severe limitations of the Google Search interface must be taken into consideration when comparing with professional literature retrieval tools.The objectives of this work are to measure the relative recall and precision of searches with Google Scholar under conditions which are derived from structured search procedures conventional in scientific literature retrieval; and to provide an overview of current advantages and disadvantages of the Google Scholar search interface in scientific literature retrieval. METHODS: General and MEDLINE-specific search strategies were retrieved from 14 Cochrane systematic reviews. Cochrane systematic review search strategies were translated to Google Scholar search expression as good as possible under consideration of the original search semantics. The references of the included studies from the Cochrane reviews were checked for their inclusion in the result sets of the Google Scholar searches. Relative recall and precision were calculated. RESULTS: We investigated Cochrane reviews with a number of included references between 11 and 70 with a total of 396 references. The Google Scholar searches resulted in sets between 4,320 and 67,800 and a total of 291,190 hits. The relative recall of the Google Scholar searches had a minimum of 76.2% and a maximum of 100% (7 searches). The precision of the Google Scholar searches had a minimum of 0.05% and a maximum of 0.92%. The overall relative recall for all searches was 92.9%, the overall precision was 0.13%. CONCLUSION: The reported relative recall must be interpreted with care. It is a quality indicator of Google Scholar confined to an experimental setting which is unavailable in systematic retrieval due to the severe limitations of the Google Scholar search interface. Currently, Google Scholar does not provide necessary elements for systematic scientific literature retrieval such as tools for incremental query optimization, export of a large number of references, a visual search builder or a history function. Google Scholar is not ready as a professional searching tool for tasks where structured retrieval methodology is necessary.
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“This research thus fills a need for support in the choice of search system, currently lacking in evidence‐synthesis methodology, and follows calls for comparative studies on the effectiveness of search systems25 or the “need to develop ‘bias profiles’ for search engines.”( 35 , p1193)”
From Which academic search systems are suitable for systematic reviews or meta‐analyses? Evaluating retrieval qualities of Google Scholar, PubMed, and 26 other resources (2020) · cites this paper as [25]
Experimental — accuracy not yet measuredThe source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“Giustini and Boulos [14] found that 5% of studies from a systematic review could not be identified using specific searches in Google Scholar, whilst Boeker et al. [11] found that up to 34% of studies from 14 systematic reviews were missed.”
From The role of google scholar in evidence reviews and its applicability to grey literature searching (2015) · cites this paper as [11]
Experimental — accuracy not yet measuredThe cited source says what the claim attributes to it.
In the citing paper
“Quality criteria have previously been used to evaluate search systems in terms of recall and precision indicating their suitability of search in general and systematic search in particular.”
The cited source says what the claim attributes to it.
In the citing paper
“Our findings support the criticism of Bramer et al,33 Bramer et al,34 and Boeker et al25 and indicate that Google Scholar's coverage and recall is an inadequate reason to use it as principal search system in systematic searches.53”
In the citing paper
“The ability of a reviewer to manipulate their search query depends on the capabilities of a search system and thus they significantly influence recall and precision.25”
In the citing paper
“Nevertheless, overall, Google Scholar's search precision has been found to be significantly lower than 1% for systematic searches.25”
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Citations
Cites
Liberati, A., Altman, D. G., Tetzlaff, J., Mulrow, C., Gøtzsche, P. C., Ioannidis, J. P. A., Clarke, M., Devereaux, P. J., Kleijnen, J., & Moher, D. (2009) · PLoS Medicine · doi:10.1371/journal.pmed.1000100 · Cited by 28,164 · cited 1×
“In a continuing discussion and agreement process, the information science and the scientific literature retrieval communities have developed methods and standards which aim for a high level of quality in literature retrieval and reporting [14-18].”
BackgroundCochrane Handbook for Systematic Reviews of Interventions: Cochrane Book Series
(2008) · doi:10.1002/9780470712184 · Cited by 25,048
Cochrane Handbook for Systematic Reviews of Interventions
Tarsilla, M. (2010) · Journal of MultiDisciplinary Evaluation · doi:10.56645/jmde.v6i14.284 · Cited by 5,232
Comparison of PubMed, Scopus, Web of Science, and Google Scholar: strengths and weaknesses
Falagas, M. E., Pitsouni, E. I., Malietzis, G. A., & Pappas, G. (2008) · The FASEB Journal · doi:10.1096/fj.07-9492lsf · Cited by 5,039 · cited 1×
“This technology known as autonomous citation indexing, is also applied to the Web of Knowledge and Scopus, however, with differing results [37,38].”
ResultA catalogue of reporting guidelines for health research
Simera, I., Moher, D., Hoey, J., Schulz, K. F., & Altman, D. G. (2010) · European Journal of Clinical Investigation · doi:10.1111/j.1365-2362.2009.02234.x · Cited by 1,047 · cited 1×
“In a continuing discussion and agreement process, the information science and the scientific literature retrieval communities have developed methods and standards which aim for a high level of quality in literature retrieval and reporting [14-18].”
BackgroundKulkarni, A. V. (2009) · JAMA · doi:10.1001/jama.2009.1307 · Cited by 821 · cited 1×
“This technology known as autonomous citation indexing, is also applied to the Web of Knowledge and Scopus, however, with differing results [37,38].”
ResultDetection of gene pathways with predictive power for breast cancer prognosis
Ma, S., & Kosorok, M. R. (2010) · BMC Bioinformatics · doi:10.1186/1471-2105-11-1 · Cited by 693
An evidence-based practice guideline for the peer review of electronic search strategies
Sampson, M., McGowan, J., Cogo, E., Grimshaw, J., Moher, D., & Lefebvre, C. (2009) · Journal of Clinical Epidemiology · doi:10.1016/j.jclinepi.2008.10.012 · Cited by 608 · cited 1×
“In a continuing discussion and agreement process, the information science and the scientific literature retrieval communities have developed methods and standards which aim for a high level of quality in literature retrieval and reporting [14-18].”
BackgroundLefebvre, C., Manheimer, E. W., & Glanville, J. (2008) · doi:10.1002/9780470712184.ch6 · Cited by 599
Selecting Studies and Collecting Data
Higgins, J. P., & Deeks, J. J. (2008) · Cochrane Handbook for Systematic Reviews of Interventions · doi:10.1002/9780470712184.ch7 · Cited by 467 · cited 2×
“Assuming fast reference checking for exclusion of irrelevant references as a first step of manual study selection [41], an experienced information specialist can check up to 1,000 references a day [53].”
Background
Research works printed but not linked: 6
- Heinzl S: Medizinreport: studien im fokus. Medizinisch-wissenschaftliche recherche: Google scholar ist PubMed möglicherweise überlegen. Dtsch Arztebl. 2012, 109: A–2467-
- Ovaska T, Fiander M, Weightman A: BMC medical informatics and decision making – user comments – is the coverage of Google scholar enough to be used alone for systematic reviews. 2013, http://www.biomedcentral.com/1472-6947/13/7/comments ,
- Cochrane Editorial Unit: Methodological expectations of Cochrane intervention reviews (MECIR). 2013, http://www.editorial-unit.cochrane.org/mecir ,
- Google Inc: About Google scholar. 2013, http://www.google.com/intl/en/scholar/about.html ,
- Jasco P: As we may search – comparison of major features of the Web of science, Scopus, and Google scholar citation-based and citation-enhanced databases. Curr Sci. 2005, 89: 1537-1547.
- The Cochrane Collaboration: The Cochrane Library. Independent high-quality evidence for health care decision making. 2013, http://www.thecochranelibrary.com/view/0/index.html ,
Cited by
Sorted by citations
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Searching the Scientific Literature and Using Systematic Reviews
Brownson, R. C., Deshpande, A. D., Gillespie, K. N., & Mazzucca-Ragan, S. (2025) · Oxford University Press eBooks · doi:10.1093/oso/9780197779637.003.0008
Tyler, D. C., Cross, J. G., & DeFrain, E. (2025) · Journal of Electronic Resources Librarianship · doi:10.1080/1941126x.2025.2581378 · Cited by 1
“…questioned the poor utility of its search interface, its failure to provide options for incremental query optimization, its occasionally incomplete recall, and its lack of options for marking and exporting large numbers of records (Boeker et al., 2013; Bramer et al., 2013; Giustini & Boulos, 2013).”
Alternative mechanisms of discovering and accessing the economics literature
Walters, W. H. (2025) · Business Information Review · doi:10.1177/02663821251413486
“Some alternative resources are constrained by the low quality of their interfaces and metadata, and this is a major problem with the two pirate sites (Boeker et al., 2013; Delgado-Quirós and Ortega, 2024; Gusenbauer and Haddaway, 2020; Walters, 2025).”
Osińska, V., Iwańska-Cieślik, B., Wojtasik, J., Buttliere, B., Karłowska-Pik, J., & Kola, A. F. (2024) · Przegląd Biblioteczny · doi:10.36702/pb.1111
The role of information in decision-making : an application to seasonal influenza vaccination policy
Silva, M.-L. (2016) · theses.fr (ABES) · doi:10.70675/9427186az1969z433dzabfczd7457ced85a5
Mapping the Heterogeneity of Emotional Design Features in Multimedia Research: A Systematic Review
Désiron, J. C., Venni, J., & Bétrancourt, M. (2026) · Educational Psychology Review · doi:10.1007/s10648-026-10138-3 · Cited by 1
“Google Scholar was discarded as it has been reported as inadequate for systematic reviews (Boeker et al., 2013, Gusen-bauer & Haddaway, 2020).”
Li, H. (2026) · Innovation journal of social sciences and economic review. · doi:10.36923/ijsser.v8i1.363
“Google Scholar was used as a supplementary search source because of its broad accessibility and its capacity to identify additional interdisciplinary and policy-oriented materials that may not always be captured consistently in conventional indexing databases (Boeker et al., 2013).”
Culture-related influences on volunteerism in later life: a conceptual framework
Lai, P. H. L., & White-Saul, B. (2026) · Quality in Ageing and Older Adults · doi:10.1108/qaoa-01-2026-0005
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Gavgani, V. Z., Oskouei, M. M., Bazdar, S., & Oghbatalab, M. (2026) · Information Discovery and Delivery · doi:10.1108/idd-02-2026-0049
Modern Approaches to Literature Search in Medicine
Namratha, N., & Narang, M. (2026) · Indian Journal of Medical Specialities · doi:10.4103/injms.injms_85_26
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Azevedo, M. L., Hall, K. C., Fernandez, M. D. S., Corrêa, G. P., & Lund, R. G. (2026) · FEBS Open Bio · doi:10.1002/2211-5463.70298
Bonadonna, G., Wroblewski, E. E., & Milich, K. M. (2026) · American Journal of Primatology · doi:10.1002/ajp.70211
“Google Scholar was used as a supplementary rather than primary search engine because of limitations in reproducibility and precision (Boeker et al. 2013; Gusenbauer and Haddaway 2020; Halevi et al. 2017).”
Reproducible study identification and selection in systematic reviews: barriers and paths forward
Lin, L., Xing, X., Wu, C., Chen, Y. T., Tong, J., McClelland, D. J., & Chen, Z. (2026) · BMJ Open · doi:10.1136/bmjopen-2026-123460 · Cited by 1
Metadata
- Authors
- Boeker, M., Vach, W., & Motschall, E.
- Affiliations
- University Medical Center Freiburg (DE)
- Corresponding author
- Boeker, Martin
- Venue
- BMC Medical Research Methodology
- Published
- 2013-10-26
- Volume
- 13
- Issue
- 1
- Pages
- 131-131
- ISSN
- 1471-2288 (ISSN-L)
- PMC
- PMC3840556
- OpenAlex
- W2073728848
- Cited by
- 225
- References
- 58
- Citations by year
- 2026: 17 · 2025: 22 · 2024: 27 · 2023: 22 · 2022: 22 · 2021: 10 · 2020: 16 · 2019: 19 · 2018: 16 · 2017: 16 · 2016: 15 · 2015: 13 · 2014: 8 · 2013: 1
- FWCI
- 13.59
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- Locations
- BMC Medical Research Methodology (publishedVersion, cc-by)
- Europe PMC (PubMed Central) (publishedVersion, cc-by)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- FreiDok plus (Universitätsbibliothek Freiburg) (submittedVersion)
- Topics
- Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
- Physical Sciences › Computer Science › Information Systems › Information Retrieval and Search Behavior
- Social Sciences › Library and Information Sciences › scientometrics and bibliometrics research
- Keywords
- Google Scholar, systematic search, search recall, search precision, search strategies, MEDLINE
- MeSH terms
- Abstracting and Indexing, Algorithms, Humans, Review Literature as Topic, MEDLINE, Internet, Data Mining, Search Engine
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