One article Becky Breedlove may want to consider is in _Serials Review_
v.19, no. 1, p. 27-30, 32-34, 62 "A Comparison of Two Methodologies for
Counting Current Periodical Use" by Maiken Naylor.  The two methods
compared were "sweep", recorded by staff, and "check off" recorded
by users.  The results indicate that user recording for the same
titles was 43% less than that of staff.  Naylor's article expands on
on an earlier one "Assessing Current Periodical Use at a Science and
Engineering Library: a dBASE III+ Application" in _SR_ 16, no.4,
(1990) p. 7-19.
   Good luck with your study!  October Ivins, LSU Libraries