A well established principle of bibliometrics is that a relatively small
number of journals get the majority of use.  A mathematical model for this
is the Bradford Distribution, stated as 1:n:n2:n3:n4. . .. (that's n, n
squared, n cubed, n to the fourth, etc.).  If n=2, then the Bradford
Distribution predicts that 1 title will get X uses, the next 2 most heavily
used will get X uses, the next 4 get X uses, the next 8 get X uses, and so
on, where X remains approximately constant.  The n (in this example 2) is
called the Bradford multiplier.

  A simpler formulation of the same phenomenon is the 80/20 rule.  It states
that 80% of use is concentrated in 20% of the titles.

  I downloaded the use statistics for the College of Saint Rose for all
abstracts viewed by our patrons in EBSCOhost databases from Jan. 2001
through May 2003, and decided to see if the Bradford Distribution and 80/20
matched the data.   They don't.

 We had 501,768 abstracts viewed from a pool of 8097 titles.  No Bradford
muliplier consistently matched the data, even though I tried grouping use
data together in a variety of ways.  The reduction in uses, if plotted,
would not be a smooth curve.  It would look more like a bumpy roller
coaster, with many changes in the rate in drop in use.  Bradford
distribution only very roughly matches the data.

  I also discovered that 11.9% of titles, not 20%, accounted for 80% of
viewed abstracts.

  Now, I've never read of anyone taking either Bradford Distribution or
80/20 as strict rules.  It's understood that no data set will match
precisely.  But these are big differences.  In the past, the gathering of
use statistics was so onerous as to force the data sets to be relatively
small, and often restricted to the journals in a single discipline.  I
wonder if the larger data samples we can now easily get require a better
model to describe the distribution of use. Models that hold for the journals
in single disciplines may not hold for interdisciplinary collections.

Steve Black
Reference, Instruction, and Serials Librarian
Neil Hellman Library
The College of Saint Rose
392 Western Ave.
Albany, NY 12203
(518) 458-5494
blacks@mail.strose.edu