[LIS-Forum] Full explanation: ‘Half-Life’ in the context of library materials. How is it calculated?

[Pawan Agrawal]

Dear library Professionals,

You must have remember about a question asked in UGC NET exam last Sunday.
We were asked a question about *half life in context of library material and
its calculation*. As per the question it's indication was about library
material and in that case we can not exclude books half life. I have browsed
a lot on this question and received a lot on citation only. cited half life,
citing half life, citation half life etc. which was covering only journal or
periodicals half life. There was almost nothing on books or other library
material. Some how I could get some hints of it and I though I must share it
with all of you. I have prepared a short answer of this question which I
feel would be useful for you.


*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.


Comments are welcome



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Thanks and Regards

------
*Pawan R. Agrawal
*Librarian
Takshshila Centre for Learning
Transpek Silox Industry Ltd.
Kalali Road- Atladra
Vadodara- 390012
Ph. 9376135580
http:\\www.grou.ps/elibrarian

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