A THEORETICAL NOTE CONCERNING THE ADAPTIVITY OF DEMAND FOR LIBRARY DOCUMENTS

DOIhttps://doi.org/10.1108/eb026648
Pages305-307
Publication Date01 April 1977
AuthorANTHONY HINDLE
SubjectInformation & knowledge management,Library & information science
DOCUMENTATION NOTE
A THEORETICAL NOTE CONCERNING THE ADAPTIVITY OF DEMAND FOR
LIBRARY DOCUMENTS
ANTHONY HINDLE
Department
of
Operational
Research,
University
of Lancaster
A NUMBER of Management Science applications in libraries have been con-
cerned with increasing the 'immediate availability' of documents held by the
library. It has been found that low availability
is
often a cause of user complaints
about library service.
All of the analyses carried out to date have assumed that the demand for docu-
ments is 'fixed' (or at least outside the librarian's control) and hence that avail-
ability will be increased by increasing the proportion of time each book spends
on the library
shelves,
by, for example, shortening loan periods. However, it has
been suggested that availability might, in
itself,
influence demand; that, for
example, an increase in availability might prompt extra demand which will
subsequently decrease availability, possibly bringing the level back to what it
was originally. Such speculation has led some to question the need to worry
about increasing document availability at all.
In a study carried out at the University of Lancaster,1 the response of the users
to an improved level of availability was observed. However, because of the wide
range of possible contributing factors a precise demand model could not be
tested. The empirical evidence is discussed in detail by Buckland2 who concludes
that 'the rise in borrowing (following the implementation of new loan policies)
represents a genuine increase in demand by the population being served in con-
sequence of
a
subjective perception by them that the service
is
more useful and
less
frustrating than previously.'
A well-known theory which can
be
used to construct
a
model of user behaviour
in this context
is
the economic theory of supply and demand where availability is
regarded as the analogue of price.
In this note a (testable) model along these lines is developed and, although not
yet validated, its qualitative characteristics are shown to be relevant to the debate
concerning the importance of actions taken to improve document availability.
THE SYSTEM STUDIED
Following Morse3 and others the library
is
assumed to be a system of documents
facing independent 'random' demands. Thus the availability of a document can
be represented
as a
function of the rate of demands
)
and the average period 'off
the shelf
(1/µ).
The parameter µ is the rate at which books are returned to the
library shelves given that they have been borrowed. For the individual document,
Immediate Availability
(A)
can be defined
as
the probability that the document is
Journal
of
Documentation,
Vol.
33,
No. 4, December
1977,
pp.
305-308
305

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