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Permalink Reply by Pawan Agrawal on December 27, 2010 at 19:12

THE EXPRESSION 'HALF-LIFE', borrowed from physics, has appeared quite frequently in the literature on documentation since 1960, when an article by Burton and Kebler1 on The 'half-life' ofsome scientific and technical literatures was published, although it had certainly been used previously.2 Burton and Kebler point out that literature becomes obsolescent rather than disintegrating (as in its original meaning), so that 'half-life' means 'half the active life', and this is commonly understood as meaning the time during which one-half of the currently active literature was published.

Defination:
The time (actual or expected) during which half the total use of individual items constituting a literature has been, or is expected to be, made.

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Permalink Reply by vijay singh on December 29, 2010 at 17:26

Half life concept in Bibliometrics

Half life is a method though to be practical for evaluating the usefulness of specific library material examines citation half life (for journals) and use half life (for
books and other material). Half life studies attempt to evaluate the length of
time in which a journal or book is used, either as resources as indicated by
citation, or physical use as indicated by circulation (books). Tsay (1998)
examines journal or book “life” based on uses as demonstrated by citation or
circulation. The premises “half life” in bibliometrics is to determine when
half of all the active literature of a field has been published, or the time
period that includes half of more of the references made. Short half life, whether
citation based or use based which means more than 50% of the use or the
citations occurred in a short period of time, implies “new volumes of a title
are generally used more often than older volumes”. Half life studies may
suggest which library resources are most used, but may also exaggerate use in
that there are more publications now than previously. There have been
suggestions that half life studies could identify which resources are least
used, resulting in a list of items for considered for discontinuation of write
off.  Caution should be taken in applying
such a plan; the mission of the institution, the orientation and the behavior
of the users, and any possible other contributors to low use, such as
inaccessibility, should be considered.

 

1995(9 citation or no item issued in a year)

1996 (6)

1997(7)

1998(6)

1999(7)

2000(7)

2001(7)

2002(3)

2003(7)

2004(5)

2005(7)

2006(2)

2007(5)

2008(2)

2009(2)

2010 (1)

 

Half life on the basis of Citation:This can be achieved by subtracting the publication year of the source documents from the median publication year of the documents that cite the
source document. We take an example of the data given above. Here, in this
example citation data is given for a certain article which was published in 1994.
In the table above the account of the citation received by the article from 1995
to 2010 is given.  Total number of documents
citing this article in period of 16 years is 83.  It is also possible that total 83 documents
are published during this period on the subject of the article published in 1994.
Now If we take out median of the publication date of citing documents it will
come 42, which is received in year 2000. Then, 2000 minus 1994 equals six
years. So the half life of the article published in 1994 would be of 6 years.

Half life on the basis of circulation: This can be achieved by subtracting the acquisition year of the source item from the median of issue years of the document. We can take an example again of the data
given above. A resource acquired by a library in the year 1995. The statistics
given above are of the circulation in the period of 16 years. Total number of
issue of this book in period of 16 year is 83 and the median as similar of the
above example comes 42, which is achieved in year 2000. Then, 2000 minus 1995
equals five year. So the half life of the item received in 1995 would be of 5
years.

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