Integrated Impact Indicators (I3) compared with Impact Factors (IFs): An alternative research design with policy implications

Loet Leydesdorff loet at LEYDESDORFF.NET
Tue Mar 29 02:56:35 EDT 2011

Integrated Impact Indicators (
<> I3) compared with
Impact Factors (IFs): 
An alternative research design with policy implications

In bibliometrics, the association of "impact" with central-tendency
statistics is mistaken. The impact of two collisions is more than the mean
or median of the two impacts; impacts add up, and citation curves should
therefore be integrated instead of averaged. For example, the journals MIS
Quarterly and JASIST differ by a factor of two in terms of their respective
impact factors (IF), but the journal with the lower IF has the higher
impact. Using percentiles (e.g., top-1%, top-10%, etc.), an integrated
impact indicator (I3) can be based on integration of the citation curves
after normalization to the same scale. The results across document sets can
be compared as percentages of the total impact of a reference set. Total
number of citations, however, should not be used instead because the shape
of the citation curves is then not appreciated. In addition to comparing I3
with IFs for the journals in two ISI Subject Categories ("Information
Science & Library Science" and "Multidisciplinary Sciences"), we show that
the summations can transparently be decomposed in terms of the contributions
of institutional units such as nations (universities, etc.) because
percentiles provide us with a paper-based measure. 


Authors: Loet Leydesdorff
<> , Lutz Bornmann

(Submitted on 27 Mar 2011; available at 


** apologies for cross-postings



Loet Leydesdorff 

Professor, University of Amsterdam
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,  <> ISTIC,
Beijing; Honorary Fellow,  <> SPRU, University
of Sussex 


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