College and Research Libraries


STEPHEN J. TURNER 

Trueswell's Weeding Technique: 

The Facts 

Recent commentary in library journals concerning Richard W. Trueswell's 
"weeding" technique provides a spectrum of opinion. The interpretations 
range from those cursing it to those applauding it. Unfortunately, too much 
of what has appeared in the literature has been in error, and to correct 
these mistakes this article reviews Trueswell' s basic method, introduces pos-
sible application areas, and addresses a number of popular misconceptions. 

RICHARD W. TRUESWELL has become a 
celebrity in library circles. This is due, at 
least in part , to some rather astonishing 
written reports based on his published work 
that deals with the use of the last circulation 
date in identifying low-circulation and -use 
books .1- 12 His approach is tantalizingly sim-
ple, can be used to slash certain circula-
tion-related system costs, and has clear im-
plications for reducing expansion costs . 
However, his work has been misunderstood 
by librarians , misinterpreted by library ad-
ministrators, and mishandled by research-
ers . 

" Poor Richard" should start his own al-
manac for publishing annual predictions of 
the curious commentary to appear over the 
next twelve months. Perhaps this paper 
would make a suitable preface for such an 
almanac as it serves to correct the record 
without discouraging constructive criticism . 

Much has been written in the recent past 
about the "Trueswell" approach and its con-
nection with . increasing performance rates 
(the proportionate amount of time a patron 
finds what is wanted when it is wanted). 
For instance, a symposium published in The 
Journal of Academic Librarianship explored 
the connection between his approach and 
the "zero-growth" concept. 1 3 

Stephen ]. Turner is with the Department of 
Finance and Management Science, School of 
Commerce, Saint Mary 's University, Halifax, 
Nova Scotia . 

134 I 

In fact, the most recent published review 
of his work appeared in these pages in the 
September 1979 issue, 14 together with a re-
joinder by Trueswell. 15 Most of these re-
ports and investigations have been "far off 
the mark" in their interpretations of Trues-
well's methods, and they have often ex-
trapolated from "facts" that Trueswell never 
established. The real facts of the matter are 
the object of this report. We can best serve 
them by starting with an introductory ex-
planation of Trueswell' s basic "technique. " 

THE FUNDAMENTALS OF 
TRUESWELL'S TECHNIQUE 

Trueswell' s technique relies upon the 
comparison of two curves that are con-
structed by calculating the time elapsed 
since the last due-date for books in circula-
tion and for books in the stacks. An illustra-
tion oft he curves is shown in figure 1. We 
can use these curves to determine the pro-
portion of books in the stacks that are re-
sponsible for satisfying any given proportion 
of the number of future circulations of books 
from the current set of books in the stacks. 
This is done by relating the points of inter-
section of the two curves with any vertical 
line as shown in figure 1. 

For example, figure 1 indicates that 96 
percent of the books currently circulating 
are being drawn from a subset of books in 
the stacks that represent only 65 percent of 
the books available for circulation. This 65 
percent of the books available for circulation 
can be identified by the fact that they all 



1.0 
0.96 

0.65 

0.5 

10 

Circulation Curve 

Stack Curve 

20 

Time in Years 

Fig. 1 
Trueswell' s Circulation Curves 

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c:l) 

"" e 
c:l) 

30 40 
;::::: 
c-..· 

~ 
c:l) 

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(J'Q -1-' 
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136 I College & Research Libraries • March 1980 

have circulated within the last ten years .. In 
our age of computerized circulation control 
systems, such identification can be done 
swiftly and at minimum expense. 

This is a splendid example of valuable op-
erations research technique. Michael Bom-
mer once wrote, "The first reason why op-
erations research has failed to achieve its 
potential in library management is that far 
too much attention has been devoted to the 
construction and solution of complex 
mathematical models. For the most part, 
these models are comprehensible only to 
operations researchers. "16 

Trueswell' s technique is a most remark-
able counterexample of this phenomenon. 
Like "a symphony on one note," his method 
is simple, straightforward, and exemplary in 
its economical use of standard information. 
The next step is to provide two examples of 
legitimate applications for Trueswell' s tech-
nique. 

THE APPLICATIONS FOR 
TRUESWELL'S TECHNIQUE 

The full ramifications of the technique are 
still being explored. However, there are at 
least two application areas where it can be 
used to substantial _benefit. 

The first of these is circulation system 
conversion. The conversion from one system 
to another typically includes systematic in-
sertion of the new checkout cards (or 
magnetic or electronically sensitive mate-
rials) in every book available for circulation. 
Trueswelr s techni9.ue shows us that this 
process can be han<Ued in a less costly fash-
ion by converting books as they return from 
circulation. Ultimately, ,his method could 
reduce relabeling cost by as much as 50 
percent with the number of books being re-
labeled stabilizing at 10 percent of current 
circulation volume (at which time relabeling 
could be conducted as books enter circula-
tion). A very important side benefit of his 
technique is that the workloads for the con-
version can be predicted for planning and 
budgeting purposes. 

The second area is the weeding of low-
circulation and low-use books. This particular 
application has been pulled into the "zero-
growth" controversy. The basic tenets of the 
zero-growth method call for pruning the 
monograph "groves" by keying on the re-
moval of low-use books (which are replaced 

by new publications) in order to avoid build-
ing new, or expanding old, facilities. 

It is best to abbreviate the introduction to 
this latter area of application, since it has 
received so much attention in the literature. 
The next section serves to clarify some of 
the more popular misconceptions in this 
area and how they can be contrasted with 
the ideas intimated by Trueswell. 

SOME MISCONCEPTIONS AND 
SOME CORRESPONDING "F ACI'S" 

Here are several of the popular miscon-
ceptions related to the use of Trueswell' s 
techniques. 

Some individuals contend that to argue 
for "no growth" is to advocate throwing out, 
for every year's acquisitions, the equivalent 
of the intake from the previous two to three 
years. The contention is that, if the annual 
publications volume keeps increasing at its 
present rate and acquisitions keep pace with 
it, then libraries will eventually end up with 
the last three years' acquisitions and nothing 
else. 17 

Unfortunately, use of the phrase "throw-
ing out" suggests th~t the books be thrown 
on some desolate dump by a pair of horny 
hands. But to most people, the idea of re-
moving a conscientiously acquired volume 
wreaks havoc with the innards. But Trues-
well's technique does. not imply weeding to 
create space you don't need. The cost of 
maintaining an empty shelf is probably not 
much different from maintaining a full one 
containing (noncirculating) books. 

However, if you do need space, then 
Trueswell' s method provides an inexpensive 
procedure for identifying little-used books, 
which are unlikely to circulate in the future. 
This does not say that the need to expand 
facilities would be eliminated, but there is 
no questioning the fact that Trueswell' s 
method would ease the financial burden in 
this area. 

In addition, Trueswell' s method keys 
upon use and not on age. Therefore, if a li-
brary decided to minimize necessary expan-
sion by employing True swell's method as 
part of the zero-growth management philos-
ophy, it would be highly unlikely that this 
library would end up with the last three 
years' acquisitions and nothing else. 

Another major concern of librarians is 
that decisions about retaining little-used 



books should be the charge of an intelligent, 
humane, book-loving librarian, and not the 
charge of some statistical computerized 
method that is coldly insensitive to the 
value of a classic or rare book. 18 

One can offer little argument on this 
point. Statistical techniques are meant to be 
filtering systems, which, in this case, funnel 
a set of books to the attention of more qual-
ified and sensitive personnel. That is, they 
are not ends in themselves as Trueswell has 
mentioned in much of his published work. 
The model allows us to reduce the cost of 
the initial filtering process (since it can be 
executed by untrained personnel) and allows 
us to guide trained personnel by calling 
their attention to books that they might 
overlook under other circumstances. 

The opposite opinion, held by some li-
brary administrators, is that Trueswell' s 
weeding technique would increase the per-
formance rate of a library. 19 We must be 
careful to realize that True swell's published 
work deals with books that circulate. That 
is, his method could be used to help 
stabilize the circulation performance rate 
(the proportion of the time a book a patron 
wants is available when it is wanted) as 
books are weeded. 

This would make room for multiple copies 
that could increase the circulation 
availability rate (proportion of the stack col-
lection on the shelf when ~ patron comes in 
looking for a circulation book). The 
circulation/performance rate could increase 
substantially as a result of purchasing the 
multiple copies. 

This sounds promising, but there is trepi-
dation, since Trueswell' s proposals have 
been published for more than twelve years 
with little practical application of his work. 
However, Marianne Cooper used Trues-
well's work to advantage at Columbia Uni-
versity when the departments of chemistry 
and chemical engineering separated and the 
serving library had to divide its collection. 20 

Other studies have been done that cite 
Trueswell' s work, but these studies cannot 
be strictly labeled as applications. 21- 23 

0rHER CRITICISMS AND 
SOME FINAL COMMENTS 

One of the more mathematically-oriented 
criticisms of Trueswell' s proposals centers 
on the idea that, apart from the items for 

Trueswelfs Weeding I 137 

obvious retention (which are easily identi-
fiable in other ways), weeding of noncore 
stock could be done at random. The idea · of 
weeding at random springs from reports 
that curves .. similar to" the ones constructed 
by Trueswell can be generated by models 
that assume random use of the books in the 
stacks. 24 

But, how can you justify use of these 
models when they imply that a book, last 
circulated twelve years ago, is valued as 
highly as one that has seen thirty circulation 
uses in the last year? The problem with the 
logic mentioned above is that the similarity 
of resulting curves does not imply the 
equivalence of the methods. 

Finally, there is a problem in interpreta-
tion. What one means by "non core'~ stock 
is highly dependent upon who is doing the 
talking. But all this is academic, because 
there are no published studies that show 
that use is uniformly distributed over any 
set of little-used titles. There are studies 
that indicate that disturbance or use of any 
type may be uniformly distributed over a 
set of little-used monographs. However, 
neither disturbance nor use is the same as .a 
circulation use which is what Trueswell has 
studied. 

Undoubtedly, this "preface" will generate 
a question or two beyond those already 
posed. However, it should be acknowledged 
that no quantitative technique for library 
management can "properly" evaluate all the 
variables in an important decision problem. 

What can be asked for are methods in 
which (a) the model sophistication is not 
beyond the comprehensibility of its users; 
(b) the model is workable in terms of neces-
sary data requirements and affordability; (c) 
the model does not ignore critical decision 
variables; and (d) the model is flexible in 
that it permits new information to alter the 
decision process· at minimum expense. It is 
interesting, indeed, that Trueswell' s method 
meets all . of the above specifications when 
used for circulation-related decisions. 

REFERENCES 

1. Richard W. Trueswell, "Two Characteristics 
of Circulation and Their Effect on the Im-
plementation of Mechanized Circulation Con-
trol Systems," College & Research Libraries 
25:~91 (July 1964). 



138 I College & Research Libraries • March 1980 

2. Richard W . Trueswell, "A Quantitative Mea-
sure of User Circulation Requirements and 
Its Possible Effect on Stack Thinning and 
Multiple Copy Determination," American 
Documentation 16:20-25 (Jan. 1965). 

3. Richard W . Trueswell, "Determining the Op-
timal Number of Volumes for a Library's 
Core Collection," Libri 16:49-60 (1966) . 

4. Richard W. Trueswell, "Analysis of Library 
User Circulation Requirements, " Final Re-
port, January 1968; supported by NSF Grant 
GN-0435. 

5. Richard W. Trueswell , "An Experiment in 
Measuring Certain Aspects of the 
Information-Searching Behavior of X-Ray 
Crystallographers, Technical Report #2 (Fi-
nal Report), " March 1968. NASA Grant 
NSG-495. 

6. Richard W. Trueswell, "Some Circulation 
Data from a Research Library," College & 
Research Libraries 29:493-95 (Nov. 1968). 

7. Richard W . Trueswell, "Some Behavioral 
Patterns of Library Users , e.g., The 80/20 
Rule ," Wilson Library Bulletin 43:458-61 
(Jan. 1969). 

8. Richard W. Trueswell, " User Circulation 
Satisfaction versus Size of Holdings at Three 
Academic Libraries ," College & Research Li-
braries 30:204-13 (May 1969). 

9. Richard W. Trueswell, "Article Use and Its 
Relationship to Individual User Satisfaction," 
College & Research Libraries 31:239-45 (July 
1970). 

10. Richard W. Trueswell, "Growing Libraries : 
Who Needs Them? A Statistical Basis for the 
No-Growth Collection, " in Daniel Gore , ed., 
Farewell to Alexandria (Westport, Conn. : 
Greenwood, Pr., 1976), p.72-104. 

11. Carol A. Johnson and Richard W. Trueswell, 
"The Weighted Criteria Statistic Score: An 
Approach to Journal Selection, " College & 
Research Libraries 39:287-92 (July 1978). 

12. Richard W. Trueswell and Stephen J . 

Turner, "Simulating Circulation-Use Charac-
teristic Curves Using Circulation Data," 
Journal of the American Society for Informa-
tion Science 30:83-87 (March 1979). 

13. "Zero Growth: When Is NOT-Enough 
Enough? A Symposium," The Journal of 
Academic Librarianship 1:4-ll (Nov. 1975). 

14. Seymour H . Sergeant, "The Uses and Limi-
tations of Trueswell: A Use Study at 
Oshkosh," College & Research Libraries 
40:416-23 (Sept. 1979). 

15. Richard W. Trueswell, "'The Uses and Limi-
tations of Trueswell': A Comment," College 
& Research Libraries 40:424-25 (Sept. 1979). 

16. Michael · Bommer, "Operations Research in 
Libraries: A Critical Assessment," Journal of 
the American Society for Information Science 
26:137--39 (May-June 1975). 

17. Maurice B. Line, Review of Farewell to 
Alexandria , College & Research Libraries 
37:556-58 (Nov. 1976). 

18. Robin Wilson, " Must We Bum Our Books?" 
Chronicle of Higher Education 12:24 (July 
12, 1976). 

19. Daniel Gore, "The View from the Tower of 
Babel," Library Journal 100:1599-1604 (Sept. 
15, 1975) . 

20. Marianne Cooper, "Criteria for Weeding of 
Collections," Library Resources & Technical 
Services 12:339-52 (Summer 1968). 

21. Stanley J. Slote, Weeding Library Collections 
(Littleton, Colo.: Libraries Unlimited, 1975), 
p.67-70. 

22. G. Travis White, "Quantitative Measures of 
Library Effectiveness, " The Journal of 
Academic Librarianship 3:128--36 (July 1977). 

23. Carol A. Seymour, "Weeding the Collection: 
A Review of Research on Identifying Obso-
lete Stock. Part I: Monographs," Libri 
22:137-48 (July 1972). 

24. J. A. Urquhart and N. C. Urquhart, Relega-
tion and Stock Control in Libraries (Stocks-
field: Oriel Pr., 1972), p .22 . 



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