[Sigmetrics] "Use of the journal impact factor for assessing individual articles need not be wrong" by Ludo Waltman and Vincent Traag

Loet Leydesdorff loet at leydesdorff.net
Fri Mar 10 06:17:56 EST 2017

re: "Use of the journal impact factor for assessing individual articles need
not be wrong" by Ludo Waltman and Vincent Traag at https://www.cwts.nl/blog.

I agree with the authors that there are two different arguments against
using the impact factor of a journal (IF) as a proxy for the quality of
papers in the journal: (1) the skewness of the citation distribution, and
(2) the ecological fallacy.

1. Against argument 1, the authors reason as follows: Let us assume (in
scenario 2, at p. 16) that "journals are relatively homogenous in terms of
the values of the articles they publish." This relatively flat distribution
of the non-observable "values" is for (unknown) statistical reasons
represented by the skewed distribution of citations to these articles. The
latter distribution can be observed. In this scenario, a journal measure
such as the journal impact factor-in other words, the mean-could be a better
predictor of the "value" of an article than its individual citation rate. 

Unlike the reasoning of others who criticize the use of the IF for the
evaluation of individual papers, the reasoning above would be free of

2. Let me add that the ecological fallacy (Robinson, 1950) does not imply
that the value of an attribute to an individual is independent of the value
at the group level, but that the latter may fail as a predictor of the
former. One loses control of the prediction: in some cases it works; in
others not. 

See: Kreft, G. G., & de Leeuw, E. (1988). The see-saw effect: A multilevel
problem? Quality and Quantity, 22(2), 127-137. 
Abstract: Studies of school effectiveness often use measures of association,
such as regression weights and correlation coefficients. These statistics
are used to estimate the size of the change or "effect" that would occur in
one variable (for example reading ability) given a particular change in
another variable (for example sex and sex ratio). In this paper we explore
the limitations of regression coefficients for use in a contextual analysis,
in which both individual and contextual variables are included as
independent variables. In our example "individual sex" and a context
variable "sex ratio of the schoolclass" are regressors, and reading ability
is the dependent variable. Our conclusion is that researchers should be
careful making interpretations of effects from multiple regression analysis,
when dealing with aggregate data. Even in the case (as in our example) when
individual and contextual variables are made orthogonal to avoid
multicollinearity, interpretation of the effects of the aggregate variable
is problematical.

See also:

.       Robinson, W. D. (1950). Ecological correlations and the behavior of
individuals. American Sociological Review, 15, 351-357. 

.       Leydesdorff, L., Wouters, P., & Bornmann, L. (2016). Professional
and citizen bibliometrics: complementarities and ambivalences in the
development and use of indicators-a state-of-the-art report. Scientometrics,
109(3), 2129-2150. 

Best wishes, 



Loet Leydesdorff 

Professor, University of Amsterdam
Amsterdam School of Communication Research (ASCoR)

 <mailto:loet at leydesdorff.net> loet at leydesdorff.net ;
<http://www.leydesdorff.net/> http://www.leydesdorff.net/ 
Associate Faculty,  <http://www.sussex.ac.uk/spru/> SPRU, University of

Guest Professor  <http://www.zju.edu.cn/english/> Zhejiang Univ., Hangzhou;
Visiting Professor,  <http://www.istic.ac.cn/Eng/brief_en.html> ISTIC,

Visiting Fellow,  <http://www.bbk.ac.uk/> Birkbeck, University of London; 



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