This document discusses bibliometrics and the impact factor calculation. It provides details on: - How the impact factor is calculated based on citations to recent articles over a two year period. - Some strengths and weaknesses of using the impact factor as a metric. - An example impact factor calculation for a journal using 2008 and 2009 citation and article data. - How Web of Science collects and analyzes journal data including bibliographic information and citation reports. - Challenges in acquiring and cleaning up Cochrane Database of Systematic Reviews citation and publication data from Web of Science. - Key findings from analyzing CDSR's citation and author data, including high author loyalty to the journal.

1. COCHRANE DATABASE OF SYSTEMATIC REVIEWS
INDEXING, CITATIONS & BIBLIOMETRICS
Adam Finch
Bibliometrics Analyst

2. Impact Factor: Meaning & Calculation
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Evaluates the impact of a journal based on a citation as a unit of quality
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Based on ISI’s Web of Science and released in an annual Journal Citation Report
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Essentially a measure of average citations per article
Impact Factor for JCR Year x = Citations in Year x to Papers from x-1 and x-2
Number of Source Items in x-1 and x-2
NB: Source Items are Articles, Reviews and Proceedings Papers; only these papers contribute to the
denominator. Citations counted on the numerator, however, can be to any document type.
Cites in 2009 to articles published in: 2008 = 2592 Number of articles published in: 2008 = 526
2007 = 3982 2007 = 637
Sum: 6574 Sum: 1163
Calculation: Cites to recent articles 6574 = 5.653
Number of recent articles 1163

3. Impact Factor: Strengths & Weaknesses
+ Average cites-per-article makes sense
+ Comparatively easy to understand
+ Can be duplicated, predicted and simulated
+ Established and recognised metric
+ Broken down into ranked subject categories
– Inconsistent standards for inclusion
– Affected by ‘ citation inflation’
– Error correction difficult
– Subject area dependency
– Self-citation open to manipulation

4. 2010 Impact Factor
The Impact Factor will probably rise next year. 2010 IF looks at 2010 cites to 2009 and 2008 papers.
2008 2009 Change
Immediacy Index 1.131 1.311 15.9%
Immediacy Index for Medicine, General & Internal 1.295 1.171 -9.6%
The Immediacy Index looks at citations in a given year to articles published in the same year.
E.g. 2009 cites to 2009 papers ÷ # 2009 papers. A rise can indicate a strong year of papers.

5. Web of Science

6. Web of Science

7. Web of Science: Journal Data
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Bibliographic data (author, address, title, keywords, etc)
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Unique identifier for article with date of publication and page numbers
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Digital Object Identifier (DOI)
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Client Article Reference (CD & Pub Numbers)
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Citation Report listing citations received each year since publication

8. Web of Science: Cochrane Database of Systematic Reviews
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Bibliographic data (author, address, title, keywords, etc)
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Unique identifier for unique article with date of publication
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Digital Object Identifier (DOI)
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Client Article Reference (CD & Pub Numbers)
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Citation Report listing citations received each year since publication

9. Web of Science: Acquiring and Repairing the Data
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Manually edit ISI article list of 2005—2008 papers so it matches actual content
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Search for and download all citations to CDSR for the past several years
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Match 15,000 citations to 2,431 target articles using:-
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Cited DOI
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Cited Article Reference
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Unique author in year
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Add Review Group data from Editorial Office records
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Download all reviews in ISI subject category and process through in-house tools
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Author 
Institution 
Citation Incidence

Document Type 
Country 
Citing Characteristics
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Region 
Review Group 
Top Cited Articles
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Analysis and reporting took days...
Data acquisition and cleanup took weeks...

10. Analysis Highlights: CDSR
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Standard analyses less useful for CDSR.
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Author loyalty. Of the 863 authors publishing reviews in CDSR that contributed to the
2009 Impact Factor, only 11 had more highly cited papers published elsewhere.
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Index comparison. Unfortunately, Elsevier’s Scopus does not provide a useful
alternative data source.
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The Scopus citation matching algorithm finds even fewer cites than WoS, despite looking at twice the
number of citing journals.

Scopus contains a larger number of duplicate version entries due to the erroneous addition of variant
Pubmed data to the records supplied by Wiley-Blackwell.

11. Analysis Highlights: CDSR

12. Analysis Highlights: CDSR

13. Analysis Highlights: Subject Category

14. Thank you
Any questions or feedback?
E-mail: burquhart@wiley.com