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Research Impact & Metrics Guide

This guide provides an introduction to research impact and an overview of select metrics used to measure research impact and their value, appropriate use, and limits.

Research Metrics: Databases

Three online sources are considered the most authoritative and comprehensive for discovering citation-based connections between scholarly articles:

Since these online sources index different journals and publications, times cited counts will vary. Overlap between these sources varies depending on the discipline. PubMed does not contain citations counts for articles (Roemer 2015).

The table summarizes select features for the three online sources for research metrics.

Feature/Online Sources Scopus Web of Science (WOS) Google Scholar Metrics
Company Elsevier Clarivate Analytics Google
Year Introduced 2004 1975 2012
Coverage Content on Scopus extends back to 1788 and references are included on records back to 1970 Content extends back to 1900 Scholar Metrics currently cover articles for the last 5 inclusive years. For 2025, includes articles published between 2020 and 2024
Content Source (refer to links below for more information)
  • Content is reviewed and selected by an independent Content Selection and Advisory Board
  • Largest collection of peer-reviewed sources (i.e., journals, books and conference papers)
  • Curated by in-house editors
  • Includes journals, books, conference proceedings
 Source – Google Scholar, primarily focusing on journal articles and selected conference papers
Content Update Frequency New source profile pages added monthly Monthly No fixed schedule
Coverage Breadth Larger coverage than Web of Science but smaller than Google Scholar Smaller coverage than Google Scholar and Scopus Broadest Coverage
Content Quality
  1. Scholarly
  2. Full text or abstract must be freely available
Journal Metrics CiteScore, SJR (SCImago Journal Rank), SNIP (Source Normalized Impact per Paper) Journal Impact Factor (JIF), Journal Citation Indicator (JCI), Eigenfactor h5-index and h5-median
Article Metrics Citation counts, FWCI (Field-Weighted Citation Impact), PlumX Metrics (altmetrics) Citation counts, Category Normalized Citation Impact h-index, h-median
Author Metrics h-index, citation counts h-index, citation counts h-index, i10-index, and total citation counts
Metrics Update Metrics, including CiteScore updated annually in June. CiteScore Tracker updated monthly. Metrics, including Journal Impact factor updated annually, usually in June Annually, usually in July
Access Subscription Based Subscription Based Free to use

References

Ball, R. (2017). Introduction to bibliometrics: new development and trends. Chandos Publishing, an imprint of Elsevier. https://www.sciencedirect.com/science/book/9780081021507

Martín-Martín, A., Orduna-Malea, E., Thelwall, M., & Delgado López-Cózar, E. (2018). Google Scholar, Web of Science, and Scopus: A systematic comparison of citations in 252 subject categories [Article]. Journal of Informetrics, 12(4), 1160-1177. https://doi.org/10.1016/j.joi.2018.09.002

Mering, M. (2017). Bibliometrics: Understanding author-, article- and journal-level metrics. Serials Review, 43(1), 41-45. https://doi.org/10.1080/00987913.2017.1282288

Roemer, R. C., & Borchardt, R. (2015). Meaningful metrics: A 21st century librarian’s guide to bibliometrics, altmetrics, and research impact. Association of College and Research Libraries, a division of the American Library Association.
Available as an Open Access Publication from ACRL