See Nancy Sprague and Mary Beth Chambers, "Full-Text Databases and the Journal Cancellation Process: A Case Study," Serials Review 26, no. 3 (2000): 19-31

AND their follow-up

Mariyam Thohira, Mary Beth Chambers, Nancy Sprague, "Full-Text Databases: A Case Study Revisited a Decade Later," Serials Review, 36, no. 3 (2010): 152-160

Their studies include thorough lit reviews and are the best sources I'm aware of for this info. Aggregated databases are not the same as publishers' online versions, but the works they cite include some cases directly relevant to your question.

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

-----Original Message-----
From: SERIALST: Serials in Libraries Discussion Forum [mailto:SERIALST@list.uvm.edu] On Behalf Of Vince Jenkins
Sent: Wednesday, November 30, 2011 2:44 PM
To: SERIALST@LIST.UVM.EDU
Subject: [SERIALST] Online issues missing content

Our reference staff have noticed that print journals to which we
subscribe occasionally include articles that are missing from the online
edition we get.  We first assumed that the online issue editors
committed errors of omission, or that maybe the authors didn't agree to
online publication of their work-- would the publishers allow that?

If so, are there statistics reporting what percentage of print journals
don't get published online?  Is there any notice provided that a given
online issue won't include the complete content of the print edition?

Thanks.

--
Vince Jenkins
Technical Services Librarian
MERIT Library, School of Education
University of Wisconsin-Madison
vjenkins at education.wisc.edu
608 262 7301 (ph)
608 262 6050 (fx)