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Vol. 3, No. 1 Fall 2005
Journal Cited Half-Life
The median age of the articles that were cited in the JCR year.
Half of a journal's cited articles were published more recently
than the cited half-life. For example, in JCR 2001 the journal Crystal
Research and Technology has a cited half-life of 7.0. That means
that articles published in Crystal Research and Technology between
1995-2001 (inclusive) account for 50% of all citations to articles
from that journal in 2001. Only journals cited 100 or more times
in the JCR year have a cited half-life. A higher or lower cited
half-life does not imply any particular value for a journal. For
instance, a primary research journal might have a longer cited half-life
than a journal that provides rapid communication of current information.
Aggregate Cited Half-Life
The aggregate cited half-life is calculated the same way as the journal cited half-life, and its
significance is comparable. For both journals and subject categories, the cited half-life is the
median age of the articles that were cited in the JCR year. The aggregate cited half-life is an
indication of the turnover rate of the body of work on a subject. For example, in JCR 2003 the subject
category Energy & Fuels has a cited half-life of 7.0. That means that articles published in Energy &
Fuels journals between 1997-2003 (inclusive) account for 50% of all citations to articles from those
journals in 2003.
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