Problems of normalization for differences in citation behavior among fields of science

Loet Leydesdorff loet at LEYDESDORFF.NET
Thu Oct 14 02:59:22 EDT 2010

Remaining problems with the  <> "New Crown
Indicator" (MNCS) of the CWTS

available at 


In their article, entitled "Towards a new crown indicator: some theoretical
considerations," Waltman et al. (2010; at arXiv:1003.2167
<> ) show that the "old crown indicator" of
CWTS in Leiden was mathematically inconsistent and that one should move to
the normalization as applied in the "new crown indicator." Although we now
agree about the statistical normalization (Optof & Leydesdorff, 2010; Van
Raan et al., 2010), the "new crown indicator" inherits the scientometric
problems of the "old" one in treating subject categories as a standard for
normalizing differences in citation behavior among fields of science. We
propose fractional counting of the citations in the citing documents as an
alternative normalization for differences in citation behavior among fields
of science.
We further note that the "mean" is not a proper statistics for measuring
differences among skewed distributions. Without changing the acronym of
"MNCS," one could define the "Median Normalized Citation Score." The median
is by definition equal to the 50th percentile. The indicator can thus easily
be extended with the 1% (= 99th percentile) most highly-cited papers. The
seeming disadvantage of having to use non-parametric statistics is more than
compensated by possible gains in the precision. 

Authors: Loet Leydesdorff
<> , Tobias Opthof


How to evaluate universities in terms of their relative citation impacts:
Fractional counting of citations and the normalization of differences among
disciplines <> 

available at 


Fractional counting of citations can improve on ranking of
multi-disciplinary research units (such as universities) by normalizing the
differences among fields of science in terms of differences in citation
behavior. Furthermore, normalization in terms of citing papers abolishes the
unsolved questions in scientometrics about the delineation of fields of
science in terms of journals and normalization when comparing among
different journals. Using publication and citation data of seven Korean
research universities, we demonstrate the advantages and the differences in
the rankings, explain the possible statistics, and suggest ways to visualize
the differences in (citing) audiences in terms of a network.

Authors: Loet Leydesdorff
<> , Jung C. Shin


** apologies for cross-postings


Loet Leydesdorff 
Amsterdam School of Communications Research (ASCoR)
Kloveniersburgwal 48, 1012 CX Amsterdam.
Tel. +31-20-525 6598; fax: +31-842239111

 <mailto:loet at> loet at ;

Visiting Professor 2007-2010,  <>
ISTIC, Beijing; Honorary Fellow 2007-2010,  <>
SPRU, University of Sussex 
Now available:
The Knowledge-Based Economy: Modeled, Measured, Simulated, 385 pp.; US$
The Self-Organization of the Knowledge-Based Society ;
The Challenge of Scientometrics


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