Impact factor and other Quality
Measurements
Vijayakumar, K. P.
Reader, DLIS
University of KeralaPage 2

Impact factor
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The impact factor (IF), is a measure of the
citations to
science and social science journals.
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It is frequently used as a proxy for the
importance of a journal to its field.
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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
publisher.Page 3

Impact factor¦
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Impact factors are calculated each year by
Thomson Scientific for those journals which
it indexes.
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The factors and indices are published in
Journal Citation Reports.
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The publication of each year covered occurs
in the summer of the following year.
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For example, impact factors for 2008 will be
published in the summer of 2009.Page 4

Impact factor¦
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The impact factor of a journal is
calculated based on a two-year period.
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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.
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For example, the 2003 impact factor of
a journal would be calculated as
followsage 5

Impact factor¦
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
2001-2
2003 impact factor = A/BPage 6

Impact factor¦
The 2003 impact factor was actually
published in 2004, because it could not
be calculated until all of the 2003
publications had been received.
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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

Impact factor¦
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These measures apply only to journals,
not individual articles or individual
scientists (unlike the H-index).
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The relative number of citations an
individual article receives is better
viewed as citation impact.Page 8

h-index
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The h-index is an index that quantifies
both the actual scientific productivity
and the apparent scientific impact of a
scientist.
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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

h-index¦
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The index can also be applied to the
productivity and impact of a group of
scientists, such as a department or
university or country.
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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

h-index¦
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Hirsch suggested that, for physicists, a value
for h of about 10-12 might be a useful
guideline for tenure decisions at major
research universities.
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A value of about 18 could mean a full
professorship, 15“20 could mean a
fellowship in the American Physical Society,
and 45 or higher could mean membership in
the
United States National Academy of Sciences.Page 11

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