CDL-Circulation as a measure of collection adequacy (Responses #1-4)

[Original posting on this subject is reproduced below; the responses follow 
it.]

From: SUSAN BEIDLER <BEIDLER_at_lycoming.edu>

I work in a small academic library serving about 1500 undergraduates and 
100 faculty.  As I have been trying to do more active assessment of our 
collection, I have been comparing our circulation figures for specific call 
number ranges/disciplines with both the number of new volumes purchased in 
those areas and the total number of volumes for that area.

What I'm wondering is if there is a generally accepted number or percentage 
of the collection's circulation that says it is adequate to meet primary 
clientele needs?

An example might make my question more clear.  Let's say that we have 2623 
books in the circulating psychology call number ranges.  Circulation last 
year for that call number range was 243, or 9.26% of the collection.  How 
do I know if that percentage of use is good or bad?

Thanks for any suggestions you can give me.

Sue Beidler
Snowden Library
Lycoming College
700 College Place
Williamsport PA 17701
  phone: 570-321-4084
fax:      570 321-4090
email: <mailto:beidler_at_lycoming.edu>beidler_at_lycoming.edu
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(1) From: "Guilfoyle, Marvin" <mg29_at_evansville.edu>

You may be asking the wrong question.  It is good that 243 books psychology 
were used­no bad about it.

I suggest that your collection adequacy might better be determined by 
Interlibrary Loan statistics.  Circulation percentage per area is useful 
for showing the areas of clientele interest, but those areas which had the 
most ILL requests to supplement what you now have are where you need to 
increase your acquisitions.

Marvin Guilfoyle
Acquisitions & Collection Development Librarian
University of Evansville Libraries
(812) 488-2247

(2) From: "Boyd, Kathryn E" <KEBoyd_at_mplib.org>

You might consider the average turnover. I hope I am doing this 
right:  2,623 volumes divided by 243 circs = average turnover (circ) of 
10.8 per volume.  And then compare this turnover with other subject areas 
of the collection.  We haven’t done this at our library yet, but it’s 
something I’ve been thinking about.  Of course, some areas will probably 
naturally circ more than others, but if there is a lot of variance in 
turnover among collections, that must mean something!  If you have really 
sophisticated reporting software, it could also look at number of unique 
titles circ’d in each subject area.  This would tell you if it’s only a few 
titles that are accounting for most of the circ or if the circ is spread 
out evenly among the collection.

Kathy Boyd
Collection Management Coordinator
Minneapolis Public Library

(3)  From: Laurie Mahaffey <mahaffey_at_ctls.net>

In the public library world, what you are talking about is “turnover rate”. 
How much of the collection turns over (circulates) in a year?

I have worked in public libraries for over 30 years, mostly in collection 
development. Those libraries with a turnover rate of 1 or above are doing 
well in matching patron needs/wants with what the collection has. Those 
with low turnover rates (below 1; the closer to 0, the worse it is) are not 
selecting the right things, or haven’t weeded in so long that no one can 
find the good with all the chaff in the way. J The busiest libraries I know 
have a turnover rate of 5 or above.

The academic library world is different. Sometimes you must retain 
everything in a discipline to get the historical perspective; public 
libraries are much more attuned to the current: what people want now, 
except for local history archives & genealogy.

How does this compare with the turnover rate in the other disciplines in 
your collection? Are the users of this portion of the collection happy with 
what they find, or are you getting a lot of requests for materials you 
don’t have? Do you have a handle on the number of ILLs you request for 
psychology (or whatever) books? Are users beginning to find what they need 
online?

Try weeding & buying some new materials, and see if circulation doesn’t 
improve in the next year.

(4) From: Linwood DeLong <linwood.delong_at_uwinnipeg.ca>
Subject: Re: CDL-Circulation as a measure of collection adequacy

This question came up on another listserv, too.   I would think that
there are no absolute percentages, but rather percentages in relation to
the circulation count as a whole, which gives you a better sense of the
use of your collection.   Sometimes circulation numbers need to be
aggregated over several years, to take into account courses that are not
offered in every academic year or term.   It's certainly an interesting
question, as is the equally frightening question "How many of the books
that I purchase as a selector actually circulate at all?", but I doubt
that there are firm answers to it.

Linwood DeLong
Collections Coordinator
University of Winnipeg Library
515 Portage Ave.
Winnipeg, MB, Canada
R3B 2E9
Ph. (204) 786-9124
FAX (204) 786-1824
e-mail:  l.delong_at_uwinnipeg.ca


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