Methods for estimating the size of Google Scholar

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 to 165 million documents. However, all the methods show considerable limitations and uncertainties due to inconsistencies in the Google Scholar search functionalities.

arXiv comment22 pages, 4 figures and 6 tables. arXiv admin note: text overlap with arXiv:1407.6239

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• Evidence of Open Access of scientific publications in Google Scholar: a large-scale analysis
• The coverage of Microsoft Academic: Analyzing the publication output of a university
• Dimensions: re-discovering the ecosystem of scientific information
• A novel method for depicting academic disciplines through Google Scholar Citations: The case of Bibliometrics
• Back to the past: on the shoulders of an academic search engine giant
• A two-sided academic landscape: portrait of highly-cited documents in Google Scholar (1950-2013)
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• Exploring usability of Reddit in data science and knowledge processing
• A review of the literature on citation impact indicators
• Subgraphs and motifs in a dynamic airline network
• A new methodology for comparing Google Scholar and Scopus
• On Low Overlap Among Search Results of Academic Search Engines
• Could freely available articles reduce faculty reliance on library for access? An analysis of items cited by faculty from Singapore Management University