Impact factor and other Quality Measurements
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14-06-2009, 09:51 AM
Impact factor and other Quality
Vijayakumar, K. P.
University of KeralaPage 2
The impact factor (IF), is a measure of the
science and social science journals.
It is frequently used as a proxy for the
importance of a journal to its field.
The Impact factor was devised by
Eugene Garfield, the founder of the
Institute for Scientific Information, now part
of Thomson, a large worldwide US-based
Impact factors are calculated each year by
Thomson Scientific for those journals which
The factors and indices are published in
Journal Citation Reports.
The publication of each year covered occurs
in the summer of the following year.
For example, impact factors for 2008 will be
published in the summer of 2009.Page 4
The impact factor of a journal is
calculated based on a two-year period.
It can be viewed as the average number
of citations in a year given to those
papers in a journal that were published
during the two preceding years.
For example, the 2003 impact factor of
a journal would be calculated as
A = the number of times articles
published in 2001-2 were cited in
indexed journals during 2003
B = the number of "citable items"
(usually articles, reviews,
proceedings or notes; not editorials
and letters-to-the-Editor) published in
2003 impact factor = A/BPage 6
The 2003 impact factor was actually
published in 2004, because it could not
be calculated until all of the 2003
publications had been received.
A convenient way of thinking about it is
that a journal that is cited once, on
average, for each article published has
an IF of 1 in the expression above.Page 7
These measures apply only to journals,
not individual articles or individual
scientists (unlike the H-index).
The relative number of citations an
individual article receives is better
viewed as citation impact.Page 8
The h-index is an index that quantifies
both the actual scientific productivity
and the apparent scientific impact of a
The index is based on the set of the
scientist's most cited papers and the
number of citations that they have
received in other people's publications.Page 9
The index can also be applied to the
productivity and impact of a group of
scientists, such as a department or
university or country.
The index was suggested by
Jorge E. Hirsch, a physicist at UCSD,
as a tool for determining theoretical
physicists' relative quality and is
sometimes called the Hirsch index or
Hirsch number.Page 10
Hirsch suggested that, for physicists, a value
for h of about 10-12 might be a useful
guideline for tenure decisions at major
A value of about 18 could mean a full
professorship, 15â€œ20 could mean a
fellowship in the American Physical Society,
and 45 or higher could mean membership in
United States National Academy of Sciences.Page 11