Leydesdorff, L; Opthof, T. 2010. Scopus's Source Normalized Impact per Paper (SNIP) Versus a Journal Impact Factor Based on Fractional Counting of Citations. JASIST. 61 (11): 2365-2369

[Eugene Garfield]

Leydesdorff, L; Opthof, T. 2010. Scopus's Source Normalized Impact per Paper 
(SNIP) Versus a Journal Impact Factor Based on Fractional Counting of 
Citations. JOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE 
AND TECHNOLOGY 61 (11): 2365-2369.

Author Full Name(s): Leydesdorff, Loet; Opthof, Tobias
Language: English
Document Type: Article
KeyWords Plus: INDICATORS; SCIENCE; TOOL

Abstract: Impact factors (and similar measures such as the Scimago Journal 
Rankings) suffer from two problems: (a) citation behavior varies among fields of 
science and, therefore, leads to systematic differences, and (b) there are no 
statistics to inform us whether differences are significant. The recently 
introduced "source normalized impact per paper" indicator of Scopus tries to 
remedy the first of these two problems, but a number of normalization decisions 
are involved, which makes it impossible to test for significance. Using fractional 
counting of citations based on the assumption that impact is proportionate to 
the number of references in the citing documents citations can be 
contextualized at the paper level and aggregated impacts of sets can be 
tested for their significance. It can be shown that the weighted impact of 
Annals of Mathematics (0.247) is not so much lower than that of Molecular Cell 
(0.386) despite a five-fold difference between their impact factors (2.793 and 
13.156, respectively).

Addresses: [Leydesdorff, Loet] Univ Amsterdam, Amsterdam Sch Commun Res 
ASCoR, NL-1012 CX Amsterdam, Netherlands; [Opthof, Tobias] Acad Med Ctr, 
Expt Cardiol Grp, Heart Failure Res Ctr, NL-1105 AZ Amsterdam, Netherlands
Reprint Address: Leydesdorff, L, Univ Amsterdam, Amsterdam Sch Commun Res 
ASCoR, Kloveniersburgwal 48, NL-1012 CX Amsterdam, Netherlands.

E-mail Address: loet at leydesdorff.net; t.opthof at inter.nl.net
ISSN: 1532-2882
DOI: 10.1002/asi.21371
fulltext: http://onlinelibrary.wiley.com/doi/10.1002/asi.21371/abstract