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Methods for estimating the size of Google Scholar

Author

Listed:
  • Enrique Orduna-Malea

    (Polytechnic University of Valencia)

  • Juan M. Ayllón

    (Universidad de Granada)

  • Alberto Martín-Martín

    (Universidad de Granada)

  • Emilio Delgado López-Cózar

    (Universidad de Granada)

Abstract

The emergence of academic search engines (mainly Google Scholar and Microsoft Academic Search) that aspire to index the entirety of current academic knowledge has revived and increased interest in the size of the academic web. The main objective of this paper is to propose various methods to estimate the current size (number of indexed documents) of Google Scholar (May 2014) and to determine its validity, precision and reliability. To do this, we present, apply and discuss three empirical methods: an external estimate based on empirical studies of Google Scholar coverage, and two internal estimate methods based on direct, empty and absurd queries, respectively. The results, despite providing disparate values, place the estimated size of Google Scholar at around 160–165 million documents. However, all the methods show considerable limitations and uncertainties due to inconsistencies in the Google Scholar search functionalities.

Suggested Citation

  • Enrique Orduna-Malea & Juan M. Ayllón & Alberto Martín-Martín & Emilio Delgado López-Cózar, 2015. "Methods for estimating the size of Google Scholar," Scientometrics, Springer;Akadémiai Kiadó, vol. 104(3), pages 931-949, September.
    • Handle: RePEc:spr:scient:v:104:y:2015:i:3:d:10.1007_s11192-015-1614-6
    DOI: 10.1007/s11192-015-1614-6
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    1. Lokman I. Meho & Kiduk Yang, 2007. "Impact of data sources on citation counts and rankings of LIS faculty: Web of science versus scopus and google scholar," Journal of the American Society for Information Science and Technology, Association for Information Science & Technology, vol. 58(13), pages 2105-2125, November.
    2. Wallace Koehler, 1999. "An analysis of web page and web site constancy and permanence," Journal of the American Society for Information Science, Association for Information Science & Technology, vol. 50(2), pages 162-180.
    3. Nigel Payne & Mike Thelwall, 2007. "A longitudinal study of academic webs: Growth and stabilisation," Scientometrics, Springer;Akadémiai Kiadó, vol. 71(3), pages 523-539, June.
    4. Réka Albert & Hawoong Jeong & Albert-László Barabási, 1999. "Diameter of the World-Wide Web," Nature, Nature, vol. 401(6749), pages 130-131, September.
    5. Joost C. F. Winter & Amir A. Zadpoor & Dimitra Dodou, 2014. "The expansion of Google Scholar versus Web of Science: a longitudinal study," Scientometrics, Springer;Akadémiai Kiadó, vol. 98(2), pages 1547-1565, February.
    6. Isidro F. Aguillo, 2012. "Is Google Scholar useful for bibliometrics? A webometric analysis," Scientometrics, Springer;Akadémiai Kiadó, vol. 91(2), pages 343-351, May.
    7. Anne-Wil Harzing, 2014. "A longitudinal study of Google Scholar coverage between 2012 and 2013," Scientometrics, Springer;Akadémiai Kiadó, vol. 98(1), pages 565-575, January.
    8. Steve Lawrence & C. Lee Giles, 1999. "Accessibility of information on the web," Nature, Nature, vol. 400(6740), pages 107-107, July.
    9. Kayvan Kousha & Mike Thelwall, 2008. "Sources of Google Scholar citations outside the Science Citation Index: A comparison between four science disciplines," Scientometrics, Springer;Akadémiai Kiadó, vol. 74(2), pages 273-294, February.
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