FW: Impact factor

Garfield, Eugene garfield at CODEX.CIS.UPENN.EDU
Fri Jul 30 13:33:24 EDT 2004

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Eugene Garfield, PhD. email:  garfield at codex.cis.upenn.edu
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-----Original Message-----
From: Garfield, Eugene
Sent: Friday, July 30, 2004 1:32 PM
Subject: RE: Impact factor

Michael Engel brings up an interesting question. The answer is yes, there
are plenty of journals that have had a decrease in impact factor. And there
is a way that you can observe increase of decrease in the latest 2003
version of the Journal Citation Reports. For each journal there is a new
"trend" graphic which shows the impact factor for the last five years.

Choosing which titles to use for illustration is not so simple. But I
decided to concentrate on the largest journals in terms of citation
frequency, not necessarily highest impact factor. Starting with the J. Biol
Chem. which is the most cited journal (384,000 cites in 2003) you can
observe that the impact factor has gone down from 7.67 in 1999 to 6.48 in
The journal CELL has gone down from 36.2 to 26.8.

One should keep in mind Robert's Matthew effect, which Manfred Bonitz has
studied with respect to journals,  which suggests that the rich get richer.
So normally one might expect that the largest journals might get an undue
increase due to the increase in the literature. After all there has been
significant growth in the number of articles published in the same five year

Some people also feel that the availability of electronic full text online
has increased citation over exclusively print media, but I feel this has not
yet been definitively proven.

I sorted the JCR file by impact factor. Most of the top journals are review
journals. The 18th journal is Nature Genetics. It started with 30.0 in 1999
and has gone down to 26.0 in 2003 which might be due to the general
phenomenon that early issues of new journals attract some hot papers but
then may taper off as the journal gets older.
The 20th journal on the list, Annual Review of Cell Biology and
Developmental Biology has gone down from 26.2 to 22.3.
Neuron has gone down from 16.7 to 14.1.

I think these examples are sufficient to give one a general idea. A
remarkable number of the top journals have a steady slight growth each year
consistent with the growth of the literature.

With best wishes. Gene Garfield

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Eugene Garfield, PhD. email:  garfield at codex.cis.upenn.edu
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-----Original Message-----
From: Michael Engel [mailto:mkengel at WEB.DE]
Sent: Friday, July 30, 2004 3:54 AM
Subject: Impact factor

One can hear everywhere that the impact factor of journals are increasing.
Are there journals where the impact factor is actually decreasing ?
(sorry, don't have access to the lists of impact factors)
Michael Engel

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