Levine-Clark, Michael, Sara Holladay, and Margaret M. Jobe, “Uniqueness and Collection Overlap in Academic Libraries,” Charleston Conference, Charleston, S.C., November 6, 2009.

1. Uniqueness and Collection
Overlap in Academic Libraries
Charleston Conference
November 6, 2009
Michael Levine-Clark
Sara Holladay
Margaret M. Jobe

2. Introduction
• Are academic libraries building diverse
collections?
• Using automated tools such as Spectra
Dimension we can:
– compare uniqueness of holdings in pre-established
consortia vs. unconnected groupings
of similar schools
– analyze percentage of uniqueness in a subject-based
analysis

3. Brief Literature Review: Unique
Titles and Duplication
• 72 ARL Libraries - Perrault (1995)
– Decline in the acquisitions rate for new imprints, 1985-
1989
– Decrease in the number of unique titles
– Increased concentration of core materials
– Conclusion: collective resource base of research libraries in
decline

4. Brief Literature Review Cont.
• Triangle Research Libraries Network - Armstrong &
Nardini (2000)
– 50 year history of cooperative collection building
– 89% of titles held by two or more libraries
– Duplication generally not caused by approval plans
• OhioLink - Kairis (2003)
– High level of duplication in the Central Catalog.
• Academic Libraries- Nardini et al (1996)
– Greater collection overlap in larger libraries.
– Significant collection overlap in history.

5. The Data
• Spectra Dimension
– Holdings and Use Data for 45 libraries
• Monographs
• Start date of 1999
• End date varies (2006-2008)
• Data from existing consortia compared to groups of
similar libraries

6. Two Liberal Arts Consortia
Institution Titles Unique Titles % Unique
(within group)
Unique Titles as %
of Local Collection
Liberal Arts 1 64,789 30,255 24.94% 46.70%
Liberal Arts 2 56,475 27,698 22.83% 49.04%
Liberal Arts 3 52,969 21,813 17.98% 41.18%
Overlap 41,553 34.25%
Institution Titles Unique Titles % Unique
(within group)
Unique Titles as %
of Local Collection
Liberal Arts 4 70,059 43,636 28.22% 62.28%
Liberal Arts 5 56,558 30,724 19.87% 54.32%
Liberal Arts 6 75,824 37,194 24.06% 49.05%
Overlap 43,055 27.85%

7. Other Liberal Arts Comparisons
Institution Titles Unique Titles % Unique
(within group)
Unique Titles as %
of Local Collection
Liberal Arts 1 64,789 34,297 22.42% 52.94%
Liberal Arts 6 75,824 40,535 26.49% 53.46%
Liberal Arts 7 67,250 32,579 21.29% 48.44%
Overlap 45,548 29.79%
Institution Titles Unique Titles % Unique
(within group)
Unique Titles as %
of Local Collection
Liberal Arts 1 64,789 32,519 21.65% 50.19%
Liberal Arts 4 70,059 37,768 25.14% 53.91%
Liberal Arts 7 67,250 37,211 24.77% 55.33%
Overlap 42,730 28.44%

8. Liberal Arts Observations
• The unconnected groups do about as well as the
two consortia:
– Overlap
• Consortium A: 34.25%
• Consortium B: 27.85%
• Liberal Arts Group A: 29.79%
• Liberal Arts Group B: 28.44%
– Unique Titles
• Consortium A: 17.98%-24.94% (average 21.92%)
• Consortium B: 19.87%-28.22% (average 24.05%)
• Liberal Arts Group A: 21.29%-26.49% (average 23.40%)
• Liberal Arts Group B: 21.65%-25.14% (average 23.85%)

9. Liberal Arts Observations
• The unconnected groups do about as well as
the two consortia:
– Unique Titles as % of Collections
• Consortium A: 41.18%-49.04% (average 45.64%)
• Consortium B: 49.05%-62.28% (average 55.22%)
• Liberal Arts Group A: 48.44%-53.46% (average 51.61%)
• Liberal Arts Group B: 50.19%-55.33% (average 52.48%)

10. Liberal Arts Observations
• Size of group may matter
– Consortium A: 121,319 titles / 34.25% overlap
– Consortium B: 154,609 titles / 27.85% overlap
– Liberal Arts Group A: 152,959 titles / 29.79%
overlap
– Liberal Arts Group B: 150,228 titles / 28.44%
overlap
• Size of institution may not
• Cooperation may not

11. Groups in a Larger Consortium
Institution Titles Unique Titles % Unique
(within group)
Unique Titles as %
of Local Collection
Doctoral 1 208,248 34,132 7.21% 16.39%
ARL 3 348,181 124,350 26.25% 35.71%
ARL 4 278,650 70,848 14.96% 25.43%
Overlap 244,355 51.59%
Institution Titles Unique Titles % Unique
(within group)
Unique Titles as %
of Local Collection
Doctoral 1 208,248 104,993 32.55% 50.42%
Doctoral 3 129,914 47,936 14.86% 36.90%
Doctoral 4 133,645 55,188 17.11% 41.29%
Overlap 114,436 35.48%

12. Groups in a Larger Consortium
Institution Titles Unique Titles % Unique
(within group)
Unique Titles as %
of Local Collection
Doctoral 3 129,914 59,067 22.18% 45.47%
Doctoral 4 133,645 71,692 26.92% 53.64%
Doctoral 5 116,799 48,800 18.32% 41.78%
Overlap 86,801 32.59%
Institution Titles Unique Titles % Unique
(within group)
Unique Titles as %
of Local Collection
Liberal Arts 7 67,250 33,809 18.71% 50.27%
Masters 1 55,848 24,688 13.66% 44.21%
Doctoral 5 116,799 72,644 40.20% 62.20%
Overlap 49,582 27.44%

13. Other Groups
Institution Titles Unique Titles % Unique
(within group)
Unique Titles as %
of Local Collection
ARL 2 359,826 172,579 28.19% 47.96%
ARL 3 348,181 104,931 17.14% 30.14%
ARL 4 278,650 69,076 11.28% 24.79%
Overlap 265,546 43.38%
Institution Titles Unique Titles % Unique
(within group)
Unique Titles as %
of Local Collection
ARL 5 196,144 83,469 21.76% 42.55%
Doctoral 1 208,248 80,633 21.02% 38.72%
Doctoral 2 172,541 72,496 18.90% 42.02%
Overlap 146,966 38.32%

14. Larger Collections = Greater Overlap
• Consortium C (1): 51.59% (473,685 titles)
• Consortium C (2): 35.48% (322,553)
• Consortium C (3): 32.59% (266,360)
• Consortium C (4): 27.44% (180,723)
• ARL Group: 43.38% (612,132)
• ARL/Doctoral Group: 38.32% (383,564)

15. Larger Collections = Greater Overlap
• Consortium C (1): 51.59% (range: 139,933)
• Consortium C (2): 35.48% (78,334)
• Consortium C (3): 32.59% (16,846)
• Consortium C (4): 27.44% (60,951)
• ARL Group: 43.38% (81,176)
• ARL/Doctoral Group: 38.32% (35,707)
(Range is difference between largest and smallest collections)

16. Unique Titles
• Consortium C (1): 7.21%-26.25% - Avg 16.14% (473,685
titles)
• Consortium C (2): 14.86%-32.55% - Avg 21.51%
(322,553)
• Consortium C (3): 18.32%-26.92% - Avg 22.47%
(266,360)
• Consortium C (4): 13.66%-40.20% - Avg 24.19%
(180,723)
• ARL Group: 11.28%-28.19% - Avg 18.87% (612,132)
• ARL/Doctoral Group: 18.90%-21.76% - Avg 20.56%
(383,564)

17. Unique Titles
• Consortium C (1): 7.21%-26.25% - Avg 16.14% (Range:
139,933)
• Consortium C (2): 14.86%-32.55% - Avg 21.51%
(78,334)
• Consortium C (3): 18.32%-26.92% - Avg 22.47%
(16,846)
• Consortium C (4): 13.66%-40.20% - avg 24.19%
(60,951)
• ARL Group: 11.28%-28.19% - Avg 18.87% (81,176)
• ARL/Doctoral Group: 18.90%-21.76% - Avg 20.56%
(35,707)

18. Size matters
• In 5/6 cases, largest collection is most unique
(exception: range=12,104, difference=.74%)
• In all cases, smallest is least unique
• In 5/6 cases, largest collection has most
unique titles as % of local collection
• In 5/6 cases, smallest collection has fewest
unique titles as % of local collection

19. Two Liberal Arts Consortia –
Subject Analysis (Am Hist – E)
Institution Titles Overlap (with
base)
% Unique
(within group)
Overlap
Liberal Arts 1 2,921 25.69% Unique to Base 37.69%
Liberal Arts 2 1,393 29.24% 8.91% Base plus one 43.55%
Liberal Arts 3 2,494 51.73% 19.34% Base plus two 18.76%
Overlap 46.06%
Institution Titles Overlap (with
base)
% Unique
(within group)
Overlap
Liberal Arts 5 2,934 30.28% Unique to Base 52.42%
Liberal Arts 4 2,360 22.63% 22.78% Base plus one 34.63%
Liberal Arts 6 2,101 37.90% 8.86% Base plus two 12.95%
Overlap 38.08%

20. Other Liberal Arts Comparisons –
Subject Analysis (Am Hist – E)
Institution Titles Overlap (with
base)
% Unique
(within group)
Overlap
Liberal Arts 1 2,921 26.18% Unique to Base 47.55%
Liberal Arts 6 2,101 34.13% 13.18% Base plus one 37.52%
Liberal Arts 7 2,656 33.24% 24.13% Base plus two 14.93%
Overlap 36.51%
Institution Titles Overlap (with
base)
% Unique
(within group)
Overlap
Liberal Arts 1 2,921 25.24% Unique to Base 47.62%
Liberal Arts 4 2,360 33.82% 16.39% Base plus one 37.69%
Liberal Arts 7 2,656 33.24% 22.07% Base plus two 14.69%
Overlap 36.30%

21. Liberal Arts Observations –
American History (E): Uniqueness
• Unique to Base Library
– Consortium A: 37.69% (27.42%, 33.24%)
– Consortium B: 52.42% (21.42%, 49.03%)
– Liberal Arts Group A: 47.55% (33.27%, 48.19%)
– Liberal Arts Group B: 47.62% (38.26%, 45.78%)
(Numbers in parentheses are the values if other
libraries in the group are the base)

22. Liberal Arts Observations –
American History (E): Overlap
• Overlap
– Consortium A: 46.06%
– Consortium B: 38.08%
– Liberal Arts Group A: 36.51%
– Liberal Arts Group B: 36.30%
• Held by Base Library and Two Others:
– Consortium A: 18.76% (21.97%, 39.34%
– Consortium B: 12.95% (16.10%, 18.09%)
– Liberal Arts Group A: 14.93% (16.42%, 20.75%)
– Liberal Arts Group B: 14.69% (16.15%, 18.18%)

23. Groups in A Larger Consortium –
Subject Analysis (Am Hist – E)
Institution Titles Overlap (with
base)
% Unique
(within group)
Overlap
ARL 3 8,535 11.70% Unique to Base 13.98%
ARL 4 7,516 75.92% 7.78% Base plus one 27.62%
Doctoral 1 6,716 68.51% 6.14% Base plus two 58.41%
Overlap 74.38%
Institution Titles Overlap (with
base)
% Unique
(within group)
Overlap
Doctoral 1 6,716 6.14% Unique to Base 9.32%
ARL 3 8,535 87.06% 11.70% Base plus one 16.45%
ARL 4 7,516 77.84% 7.78% Base plus two 74.23%
Overlap 74.38%

24. Groups in A Larger Consortium –
Subject Analysis (Am Hist – E)
Institution Titles Overlap (with
base)
% Unique
(within group)
Overlap
Doctoral 1 6,716 25.88% Unique to Base 35.82%
Doctoral 3 3,485 36.42% 7.89% Base plus one 41.80%
Doctoral 4 5,215 50.13% 16.59% Base plus two 22.38%
Overlap 49.64%
Institution Titles Overlap (with
base)
% Unique
(within group)
Overlap
Doctoral 4 5,215 34.74% Unique to Base 51.39%
Doctoral 3 3,485 34.67% 17.19% Base plus one 35.09%
Doctoral 5 2,605 27.46% 10.66% Base plus two 13.52%
Overlap 37.41%

25. Groups in A Larger Consortium –
Subject Analysis (Am Hist – E)
Institution Titles Overlap (with
base)
% Unique
(within group)
Overlap
Doctoral 5 2,605 27.69% Unique to Base 50.83%
Liberal Arts 7 2,656 40.42% 27.19% Base plus one 35.55%
Masters 1 1,459 22.38% 11.98% Base plus two 13.63%
Overlap 33.14%
Institution Titles Overlap (with
base)
% Unique
(within group)
Overlap
Liberal Arts 7 2,656 27.19% Unique to Base 48.95%
Doctoral 5 2,605 39.65% 27.69% Base plus one 37.69%
Masters 1 1,459 24.77% 11.98% Base plus two 13.37%
Overlap 33.14%

26. Other Groups –
Subject Analysis (Am Hist – E)
Institution Titles Overlap (with
base)
% Unique
(within group)
Overlap
ARL 2 8,090 14.46% Unique to Base 20.01%
ARL 3 8,535 76.98% 8.11% Base plus one 17.19%
ARL 4 7,516 65.80% 7.09% Base plus two 62.79%
Overlap 70.34%
Institution Titles Overlap (with
base)
% Unique
(within group)
Overlap
Doctoral 1 6,716 14.08% Unique to Base 20.19%
ARL 5 5,643 60.99% 9.01% Base plus one 33.14%
Doctoral 2 6,448 65.49% 14.23% Base plus two 46.66%
Overlap 62.68%

27. American History Comparisons -
Conclusions
• Research Libraries - not as unique as one
would expect?
– Overlap:
• ARL/Doctoral Group (Consortium): 74.38%%
• Doctoral Groups (Consortium): 49.64%/37.41%
• Smallest Group: 33.14%
• ARL Group: 70.34%
• ARL/Doctoral Group: 62.68%

28. American History Comparisons -
Conclusions
• Research Libraries - not as unique as one
would expect?
– Base + Two:
• ARL/Doctoral Group (Consortium): 58.41%/74.23%
• Doctoral Groups (Consortium): 22.38%/13.52%
• Smallest Group: 13.63%/13.37%
• ARL Group: 62.79%
• ARL/Doctoral Group: 46.66%

29. American History Comparisons -
Conclusions
• Research Libraries - not as unique as one
would expect?
– Most Unique Collection:
• ARL/Doctoral Group (Consortium): 11.70%
• Doctoral Groups (Consortium): 25.88%/34.74%
• Smallest Group: 27.69%
• ARL Group: 14.46%
• ARL/Doctoral Group: 14.23%

30. Conclusion
• Consortial agreements do not seem to lead to
decreased overlap.
• Larger libraries duplicate each other more than do
smaller libraries.

31. Future directions
• Detailed subject analysis.
• Comparative analysis of use.
• Survey of libraries contributing holdings
information to Spectra Dimension about
collection development patterns.
• Overview of local programs/curricula.

32. References
• Kim Armstrong and Bob Nardini, “Making the
Common Uncommon? Examining Consortial
Approval Plan Cooperation,” Collection
Management 24, no. 1-2 (2000):87-105.
• Rob Kairis, “Consortium Level Collection
Development: A Duplication Study of the
OhioLINK Central Catalog,” Library Collections,
Acquistions, & Technical Services 27
(2003):317-326.

33. References Cont.
• Robert F. Nardini, Charles M. Getchell, Jr., and
Thomas E. Cheever, C. M. Getchell, “Approval
plan overlap: A study of four libraries,”
Acquisitions Librarian 16 (1996): 75-97.
• Anna H. Perrault, “The Changing Print
Resource Base of Academic Libraries in the
United States,” Journal of Education for Library
and Information Science, 36 (Fall 1995):295-
308.

34. Michael Levine-Clark
michael.levine-clark@du.edu
Sara Holladay
sara.holladay@gmail.com
Margaret M. Jobe
margaret.jobe@colorado.edu