The ARL Membership Criteria Index is a summary measure of relative size among the university library
members of the Association and its sole purpose is to serve as a membership criterion that is quantitative in nature in
addition to other qualitative evidence. Both qualitative and quantitative factors support the assessment of research
libraries within the Association.
The five variables used in the index were determined by factor analysis of 22 variables originally and
represent the elements in which ARL university libraries most resemble one
They do not attempt to
measure a library’s services, quality of collections, or success in meeting the needs of users; in comparing any
individual library to ARL medians or other ARL members, evaluations must always be made within the context of
local goals and characteristics.
The index is calculated using five data elements:
number of volumes held
number of volumes added (gross)
number of current serials received
total operating expenditures
number of professional plus support staff
The index scores are rounded to three decimal places, which may give the appearance of identical scores
(and thus ranks) for some institutions; in fact, when the complete principal component score is calculated, it is
extended to at least five places. Each institution has a unique result and place in the rank order. Information about
index scores and formulae from earlier years as well as excel versions of the index tables are available at:
The formula for 2004-05, based upon the 34 founding members,
. 449766 x log of volumes held
+ . 365633 x log of volumes added (gross)
+ . 476575 x log of current serials
+ . 489405 x log of total library expenditures
+ . 494003 x log of total professional plus support staff
- 27.639982
Decisions on membership issues are being dealt by the ARL Membership Committee which has the
responsibility for articulating the principles and tenets of ARL membership, reviews membership criteria,
recommends new members to the Board for approval by the full membership, and reviews and makes
recommendations on membership status. Principles and procedures for Membership in the Association of Research
Libraries are available at http://www.arl.org/stats/qualcov.html . For more information on the ARL Membership
Committee agenda, please contact Julia Blixrud, Assistant Executive Director, External Relations (jblix@arl.org).
For any questions regarding the methodology used to develop the ARL membership criteria index or any other
aspect of the ARL Statistics and Measurement Program, contact Martha Kyrillidou (martha@arl.org).
The 5-variable index was adopted as a membership criterion in May 1987 by the ARL membership. Previous membership criteria were based
on a 10-variable index, which had been adopted by the membership in May 1980. The elements used in the 10-variable index were: (1) number
of volumes held, (2) number of volumes added (gross), (3) number of microform units held, (4) number of current serials received, (5)
expenditures for library materials, (6) expenditures for binding, (7) total salary and wage expenditures, (8) other operating expenditures, (9)
number of professional staff, and (10) number of support staff.
“log” refers to the natural logarithm, [ ln ].
Previous Page Next Page