A presentation on new bibliometric indicators such as h-index, eigenfactor, SNIP, SJR, Publish or Perish; and the use of Google Scholar and Scopus for citation analysis.

1. Bibliometrics:
From Garfield to Google Scholar
Elaine M. Lasda Bergman
University at Albany
Upstate NY SLA Spring Meeting
April 20, 2012

2. What we’re going to cover
• What is the study of Bibliometrics?
• Bibliometrics which assess entire Journals
– JIF, Eigenfactor, SNIP, SJR
• Bibliometrics assessing authors, articles,
institutions
– citation count, H-index, e-index, etc. etc. etc.

3. What is bibliometrics?
• Scholarly communication:
Eugene Garfield tracing the history and
evolution of ideas from one
scholar to another
• Measures the scholarly
influence of articles,
journals, scholars,
institutions

4. Three sources for citation data

5. Three sources for citation data
• Citation data overlaps, but not completely
• Unique citing references in all three databases
• Unique metrics developed using each
database
– Metrics could be computed in any one of these
but most are tied to a particular source

6. JOURNAL METRICS

7. What is measured?
• Journal Ranking
– “Quality” or “Importance” of journal relative to
other journals
• Usually within a given field of study
• There are many ways to measure “quality,”
“importance”

8. “Impact”
• Journal Impact Factor (JIF)
• Web of Science – Journal Citation Reports
• Basically “how fast are ideas spreading from
this journal to other publications?”
• Formula is a ratio:
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

9. Journal Impact Factor
• Journal of Hypothetical Examples
Citing references appearing in
100 2010, to articles published in
Journal in 2009 and 2008
Total number of articles
200 in Journal published in
2009 and 2008
0.50 JIF

10. Concerns with impact factor
• 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”?

11. “Influence”
• Eigenfactor.org
• Web of Science: Journal Citation Reports
• Eigenvector analysis: Similar to Google
PageRank, “chain of citations”
• Takes into account the total amount of
“citation traffic” appearing in JCR
Influence of the citing journal,
Divided by the total number of citations
appearing in that journal.

12. “Influence”
• 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

13. Considerations
• 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.
– Correlation to the JIF

14. Examples
• For the year 2011, Neurology had an eigenfactor
score of .159. This number = % of all citation
traffic of articles in the JCR
• For the year 2011, Neurology had an article
influence score of 2.57. This means an average
article in this journal is roughly 2 ½ X more
influential than an average article in all of JCR
• www.eigenfactor.org

15. “Citation Potential”
• SNIP: Source Normalized Impact Per Paper
• Uses Scopus data
• Citation Potential = total number of citing
references in all journals which have cited this
journal
• Takes an average citation count
The ratio of the journal’s average citation count per
paper to the citation potential in its subject field

16. Pros and cons of SNIP
• Can compare SNIP scores across disciplines
• Aggregate of a journal, so larger journals
automatically have higher scores than smaller
journals

17. “Prestige”
• SJR: Scimago Journal Rank
• Uses Scopus data
• Measures “current average prestige per
paper”
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.

18. Pros and Cons of SJR
• 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
• http://www.scimagojr.com/

19. Examples in Scopus

20. Examples in Scopus

21. Examples in Scopus

22. Examples in Scopus

23. Examples in Scopus

24. Examples in Scopus

25. METRICS FOR SCHOLARS,
AUTHORS, INSTITUTIONS, ETC.

26. Citation count
• Number of times cited within a given time
period
– Journals, Authors, Articles, etc.
• Does not take into account
– Materials not included in citation database
– Self citations
– Variations in citation patterns/rates

27. Citation count
• Citation counts will vary depending on which
database you use
• It is very difficult to get a complete count of all
citing references

28. H-index
• Scopus, Google Scholar, WoS?
• Meant to account for differences in citation
patterns (i.e., “one-hit wonders” vs. consistent
record of scholarship)
“A scientist has index h if h of his/her Np
papers have at least h citations each and the
other (Np-h) papers have no more than h
citations each” (Hisrch 2005)

29. H-index Example
30
Scholar A Scholar B
10 27
25
10 12
9 5
20 8 4
7 4
Number of Citations
H-index 6 2
15
Scholar A 6 2
Scholar B
10 56 citations 56 citations
6 h-index 4 h-index
5
0
1 2 3 4 5 6 7
Article Number

30. Variations on the H-index
• G-index (Egghe 2006): gives greater weight to highly cited articles
– The top g number of articles have received a combined total of
g2 citations
• E-index (Zhang 2009): gives greater weight to highly cited articles
– The square root of the surplus of citations in the h-set beyond
h2
• Contemporary h-index (Sidiropolous, et. Al. 2006): gives greater
weight to newer articles
– “parameterized”: current year, citations count 4 times, four
years ago, citations count 1 time, 6 years ago, citations count
4/6 times

31. Variations on the H-index
• Individual h-index (Batista, et al. 2006)accounts for co-authors
– Divides the h-index by the average number of authors per paper
• Alternative individual h-index (Harzing): accounts for co-authors
– Normalizes citation counts: divides # of citations by average # of
authors per each paper and then computes the h-index
• Another alternative individual h-index (Schreiber 2006):
accounts for co-authors
– Divides by fractions of papers instead of # of authors, keeps full
citation count

32. Variations on the H-index
• Age weighted citation rate and AW index (Jin
2007): accounts for variations in citation
patterns over time
– AWCR= The square root of the sum of all age-weighted citation
counts over all papers that contribute to the h-index
– AW-index= the square root of the AWCR
– Per-author AWCR: AWCR divided by number of authors for each
paper

33. Publish or Perish
• Google scholar citation information
• Interdisciplinary topics, fields relying on
conference papers or reports
• Greatest variety of metrics
• Dirty data
• Unverified data
• Nonscholarly sources

34. Differences in H-index
Scopus vs. Google Scholar (PoP)
The Case of Eugene Garfield

35. PoP Interface

36. PoP Search for Garfield

37. PoP Search for Garfield

38. An aside:
Why I don’t like PoP for Journal Metrics

39. Scopus Search for Garfield

40. Scopus Search for Garfield

41. Scopus Search for Garfield

42. Scopus Search for Garfield

43. Scopus Search for Garfield
Citation overview

44. Scopus Search for Garfield
Link to graphic
information next to
citation overview

45. Scopus Search for Garfield

46. Scopus Search for Garfield

47. Scopus Search for Garfield

48. Google scholar citations
http://scholar.google.com/intl/en/scholar/citations.html

49. Microsoft Academic
http://academic.research.microsoft.com/

50. Considerations
• Don’t measure an individual article’s impact by the
metrics for the entire journal
• Do I need a comparison within a discipline or across
disciplines?
• Does the citation pattern matter or just the count?
• Does the database being used cover my subject as
thoroughly as possible?
• To what degree does my subject area rely on non-
journal scholarly publications?
• Not all citing references are positive!

51. Questions??
Elaine Lasda Bergman
elasdabergman@albany.edu