Percentage of Grey/Gray Literature By Field/Discipline

 I am greatly interested in studies that have calculated the relative
percentage of a discipline's literature that is considered grey/gray
literature.

A fabricated example:
Overall the literature of agronomy is 40% gray/grey literature
[CITE]

GRAY LITERATURE DEFINED
[ http://www.moyak.com/researcher/resume/papers/var7mkmkw.html ]

"M. C. Debachere has written that it is easier to describe, rather than
define grey literature. Collectively the term covers an extensive range of
materials that cannot be found easily through conventional channels such
as publishers, "but which is frequently original and usually recent"
(Debachere 1995,94). Peter Hirtle in Broadsides vs. Grey Literature
defines it as:

The quasi-printed reports, unpublished but circulated papers, unpublished
proceedings of conferences, printed programs from conferences, and the
other non-unique material which seems to constitute the bulk of our modern
manuscript collections (Hirtle 1991)."

[ http://www.moyak.com/researcher/resume/papers/var7mkmkw.html ]

  To such an amorphous list, one may also wish to add Web/Internet
resources, most notably e-prints (of course).

NOTE:  I am *particularly* interested in the Gray/Grey Literature of
Psychology.

 [I've just begun a literature review but thought I'd also tap The Wisdom
of the Web as well]

  As Always, Any and All contributions, suggestions, comments, queries,
questions, basketball coaches, or Cosmic Insights are Most Welcome.

/Gerry

Gerry McKiernan
Gray/Grey Librarian
Iowa State University
Ames IA 50011

gerrymck@iastate.edu