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BASIC CITATION
METRICS:
AN OVERVIEW
WHAT DO BIBLIOMETRICS
MEASURE?
Eugene Garfield
“Father of Citation Analysis”
• Scholarly communication: tracing the histor...
SOURCES OF
CITATION
DATA AT
UALBANY
• UAlbany subscription is 1993-present
• Pre-1993 data is available in print volumes –...
• Many subject specific
databases also include cited
reference information.
• There will be overlap in
coverage of differe...
• Journal coverage unknown, sporadic
– Whatever the web crawler can “read”
• No quality control process
• Better coverage ...
• Citation data overlaps in all
sources, but not completely
• Unique citing references in
all databases
• Unique metrics d...
• Citation Count
• Journal Impact Factor
• Eigenfactor
• H-index
• SNIP
• SJR
METRICS
• Number of times cited in
scholarly journals indexed in a
particular resources
• Citation count metric does
not take into...
• Found in: Web of Science –
Journal Citation Reports
• Essential concept: “how fast
are ideas spreading from this
journal...
Journal of Hypothetical ExamplesJOURNAL
IMPACT
FACTOR
Citing references appearing in
2010, to articles published in
Journa...
• Cannot be used to compare
across disciplines
• Two year time frame not
adequate for social sciences,
humanities
• Covera...
• Found in:
– eigenfactor.org
– Web of Science: Journal
Citation Reports
• Essential concept: Takes into
account the total...
• Journal Impact
Factor:
– All citing references weighted
equally
• Eigenfactor:
– SOME CITING REFERENCES ARE
MORE IMPORTA...
• Eigenfactor will always be
bigger if a journal is larger,
i.e., publishes more articles
• Article Influence Score:
corre...
H-INDEX
http://proj.ncku.edu.tw/research/commentary/e/20080815/images/0808110317430yfDpK.jpg
• Found in:
• Many citation a...
0
5
10
15
20
25
30
1 2 3 4 5 6 7
NumberofCitations
Article Number
H-index
Scholar A
Scholar B
H-INDEX
EXAMPLE
Scholar A Sc...
• Found in:
– www.journalmetrics.com
– Scopus
• Essential concept: Citation
Potential: total number of
citing references i...
• Can compare SNIP scores
across disciplines
• Aggregate of a journal, so
larger journals automatically
have higher scores...
• Found in:
– www.scimagojr.com
– Scopus data
• Essential Concept: measures “current
average prestige per paper”
• Formula...
• Corrects for self citations
• Correlated to JIF
• Scores can be compared
across disciplines
• Web version provides
data ...
• Journal quality ≠ article quality
• Citing a work ≠ agreement with
that work
• Self citations: including them is
controv...
• Is a trend analysis of scholarly
influence over time needed, or
simply a count of total citations?
• Does the database a...
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Overview of Citation Metrics

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An over view of various bibliometric indicators, how they are computed, and where they can be found.

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Overview of Citation Metrics

  1. 1. BASIC CITATION METRICS: AN OVERVIEW
  2. 2. WHAT DO BIBLIOMETRICS MEASURE? Eugene Garfield “Father of Citation Analysis” • Scholarly communication: tracing the history and evolution of ideas from one scholar to another • Measures the scholarly influence of articles, journals, scholars, institutions Photo: http://www.chemheritage.org/Discover/Collections/Oral-Histories/Details/asset_upload_file66_69008_thumbnail.jpg
  3. 3. SOURCES OF CITATION DATA AT UALBANY • UAlbany subscription is 1993-present • Pre-1993 data is available in print volumes – Ask A Librarian! • Currently covers over 12,000 journals • Journals undergo quality review process prior to inclusion • Weak in conference proceedings, books, data repositories • Master Journal List of Web of Science
  4. 4. • Many subject specific databases also include cited reference information. • There will be overlap in coverage of different databases on a cover, take care to identify/remove duplicate citations. • See Subject Specific Databases on this guide for more information on these resources. SOURCES OF CITATION DATA
  5. 5. • Journal coverage unknown, sporadic – Whatever the web crawler can “read” • No quality control process • Better coverage of – conference proceedings – foreign language articles – Nontraditional publication sources (blogs, reports, white papers) – Theses and dissertations • Coverage roughly from 1996-present; some older but inconsistent SOURCES OF CITATION DATA
  6. 6. • Citation data overlaps in all sources, but not completely • Unique citing references in all databases • Unique metrics developed using each major database WHAT’S THE DIFFERENCE?
  7. 7. • Citation Count • Journal Impact Factor • Eigenfactor • H-index • SNIP • SJR METRICS
  8. 8. • Number of times cited in scholarly journals indexed in a particular resources • Citation count metric does not take into account: – Materials not included in citation database – Sometimes self citations are eliminated from count CITATION COUNT
  9. 9. • Found in: Web of Science – Journal Citation Reports • Essential concept: “how fast are ideas spreading from this journal to other publications?” • Formula: JOURNAL IMPACT FACTOR Number of citations to a journal in a given year from articles occurring in the past 2 years, divided by the number of scholarly articles published in the journal in the past 2 years
  10. 10. Journal of Hypothetical ExamplesJOURNAL IMPACT FACTOR Citing references appearing in 2010, to articles published in Journal in 2009 and 2008 100 200 Total number of articles in Journal published in 2009 and 2008 0.50 JIF
  11. 11. • Cannot be used to compare across disciplines • Two year time frame not adequate for social sciences, humanities • Coverage of some disciplines not sufficient in Web of Science • Is a measure of “impact” a measure of “quality”? CONCERNS WITH JIF
  12. 12. • Found in: – eigenfactor.org – Web of Science: Journal Citation Reports • Essential concept: Takes into account the total amount of “citation traffic” appearing in JCR • Formula: EIGENFACTOR Influence of the citing journal, Divided by the total number of citations appearing in that journal.
  13. 13. • Journal Impact Factor: – All citing references weighted equally • Eigenfactor: – SOME CITING REFERENCES ARE MORE IMPORTANT THAN OTHERS • The citing articles from journals that are heavily cited themselves demonstrate greater influence ESSENTIAL DIFFERENCES: JIF & EIGENFACTOR
  14. 14. • Eigenfactor will always be bigger if a journal is larger, i.e., publishes more articles • Article Influence Score: corrects for journal size – takes the journal’s Eigenfactor score and further divides it by the number of articles in the journal. – Correlated to the JIF CONSIDER THE FOLLOWING
  15. 15. H-INDEX http://proj.ncku.edu.tw/research/commentary/e/20080815/images/0808110317430yfDpK.jpg • Found in: • Many citation analytics sources • Web of Science • Google Scholar Citations • Etc… • Essential Concept: Identifies a sustained record of multiple publications that have been cited frequently • Formula: The maximum number of articles h, such that each has received at least h citations. Jorge E. Hirsch
  16. 16. 0 5 10 15 20 25 30 1 2 3 4 5 6 7 NumberofCitations Article Number H-index Scholar A Scholar B H-INDEX EXAMPLE Scholar A Scholar B 10 27 10 12 9 5 8 4 7 4 6 2 6 2 56 citations 56 citations 6 h-index 4 h-index
  17. 17. • Found in: – www.journalmetrics.com – Scopus • Essential concept: Citation Potential: total number of citing references in all journals which have cited this journal • Formula: SNIP: SOURCE NORMALIZED IMPACT PER PAPER The ratio of the journal’s average citation count per paper to the citation potential in its subject field
  18. 18. • Can compare SNIP scores across disciplines • Aggregate of a journal, so larger journals automatically have higher scores than smaller journals PROS AND CONS OF SNIP
  19. 19. • Found in: – www.scimagojr.com – Scopus data • Essential Concept: measures “current average prestige per paper” • Formula: SJR: SCIMAGO JOURNAL RANKING Prestige factors include: # of journals in the Scopus database, # of articles in Scopus from this journal, citation count, eigenvector analysis of important citing references, corrections for self-citations, and normalization by the number of significant works published in the journal.
  20. 20. • Corrects for self citations • Correlated to JIF • Scores can be compared across disciplines • Web version provides data on countries • Three year window not good for social sciences PROS AND CONS OF SJR
  21. 21. • Journal quality ≠ article quality • Citing a work ≠ agreement with that work • Self citations: including them is controversial • Variance in citation patterns from domain to domain KEEP IN MIND
  22. 22. • Is a trend analysis of scholarly influence over time needed, or simply a count of total citations? • Does the database adequately cover the key journals in my subject domain? • Are there significant works in my domain that are not peer reviewed, scholarly journals (such as conference proceedings, government reports, etc.) KEEP IN MIND

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