Lionel,

I similarly have never seen an official definition, but can suggest two
working definitions (each of which has a different purpose)

a) The catchment area of library A is that area from which users
habitually travel to visit library A.
b) The catchment area of library A is that area from which more users
travel to visit library A than to visit library B, library C, etc

Definition (a) reflects the total impact of library A, but catchment
areas will overlap considerably, and if you add together the populations
of all your catchment areas the total can be anything up to double the
population of your authority. Thus when it comes to arguing for the
resources needed to support all your libraries, the accusation of
"double counting" becomes indefensible.

Definition (b) is better suited to the task of apportioning resources
between your libraries, but when you consider the catchment areas in
isolation, some will look very odd.

It is not unusual, using the definition (a), for the catchment area of
library B to be wholly subsumed within that of library A, because A's
users spread right across B's area, but at a lower density, and this can
produce misunderstandings in the mind of an inexpert observer.

The situation becomes particularly difficult when it comes to looking at
your Central Library, which almost certainly serves two functions -
firstly as the local library for its immediate area and secondly as a
more specialised resource for the entire authority. Thus catchment area
(a) will contain your entire population, whilst (b) might be quite
small.

All in all, I would say that the catchment area debate is a triumph of
art over science. Some years ago, when, as a result of a re-structuring,
we had a member of staff with a few weeks to spare, I produced a random
10% sample of our entire borrower file, sorted it by library, post-code
and house number, and gave the huge chunk of print-out to the poor chap
with a big map, an A-Z and a set of coloured pens (one colour for each
library). The result really is a work of art - stand close and it is
just a maze of dots like an impressionist painting - move back so that
the dots start merging and it begins to take life. You can see what it
happening, and how geographical features like railways and major roads
have an impact on people's behaviour. Unfortunately this old kind of
professional judgement based on subjective impressions is a bit out of
date now, and people seem to prefer facts even if reality has to be
stretched to arrive at them, but looking back, the map has been used
time and time again for different purposes, and I am bound to say that
the exercise was worth it.

Sent in the hope that it might prompt some further debate.....

Peter Marshall
Project Development Librarian
Bexley Council
Tel: 020 8320 4135 (Direct Line)
email: [log in to unmask]
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-----Original Message-----
From: Lionel Aldridge [mailto:[log in to unmask]]
Sent: 17 January 2003 11:06
To: [log in to unmask]
Subject: Library Catchment areas


Can anyone help with a practical  & preferably accepted definition of a
catchment area?
We like many others are continually doing community profiles for
libraries,
trying to match Plus & user data with these, etc, but sometimes I feel
that
it is all groping in the dark & question the meaning of the figures I
pull
out. I have been using postcode information to draw out differences
between
libraries but there are problems, users from miles away who use the
library
in their lunch hour, children visiting with Gran, etc. Defining by
distance
doesn't allow for geographical factors which we all know influence use
(motorways, hills, etc) although the public library standards assume
this
is paramount.
I'm not sure I've ever seen a definition of a catchment area apart from
ones we've made up ourselves so perhaps I should leave out the word
accepted in my 1st sentence.
Lionel Aldridge
Leeds Library & Information Services



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