DUPLICATION IN UNION CATALOGUES
| Date | 01 April 1973 |
| Pages | 373-379 |
| Published date | 01 April 1973 |
| DOI | https://doi.org/10.1108/eb026563 |
| Author | W.Y. ARMS |
| Subject Matter | Information & knowledge management,Library & information science |
DUPLICATION IN UNION CATALOGUES
W. Y. ARMS
Faculty
of
Mathematics,
The Open
University,
Milton
Keynes
This paper uses
figures
of the overlap between eighteen libraries to develop a
mathematical model of the duplication likely in a union catalogue. Two
consequences-come from the model, that the percentage of unique items held
by a library depends on the type of the library rather than on
its
size,
and that
for a homogeneous group of libraries the proportion of new titles added
when extra entries are made to the catalogue tends to a value greater than
zero.
These consequences, which are supported by further data, suggest that
the law of diminishing returns is much weaker than might be expected when
building up a union catalogue.
INTRODUCTION
DESPITE THE SUCCESS of the collections maintained by the National
Lending Library and National Central Library, union catalogues are likely
to remain important for both interlibrary lending and reference
use.
Union
catalogues are particularly valuable for locating older and foreign language
items holdings of which are widely scattered over many
libraries.
The costs
of building up and maintaining large catalogues arc so great that for the
design of
a
union catalogue it is useful to know the overlap of holdings
between various libraries which might contribute to the catalogue. With
this information, decisions can be made whether to concentrate on in-
cluding the holdings of a large number of specialist libraries, or a smaller
number of large research libraries, and to estimate the number of new titles
which will be added to the catalogue if a given number of new entries are
made.
For the National Libraries ADP Study, the University of Lancaster
Library Research Unit carried out two studies of the collections of eighteen
national and research libraries1,2. The first of these studies looked at the
overlap between holdings of pre-1967 monographs and the second at the
overlap of acquisitions of foreign (non-British) monographs. The first of
these studies is of particular interest for the design of union catalogues. The
method used was to take a random sample from the catalogues of each
library and then to search the catalogue of the other libraries for each item
in the
sample.
That
is
the study compared catalogue overlap rather than the
actual holdings.
The eighteen libraries and the estimated
size
of their monograph holdings
are given in Table 1. All the most important British libraries were included
373
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