Federal Depository Libraries receive material from GPO that they request at no cost.
Not all federal libraries are federal depositories and many depository collections are housed in academic or other non-federal libraries.
A library has to go through an application process and be accepted before it can be a part of the depository program. Once part of the program, there are specific laws/rules that must be followed in order for the library to maintain depository status.
In the past 3 years much of my serial collection is no longer available to me in print. Because of large budget cuts, GPO has limited much of the print serial collection, and provides this material to depositories in electronic format only.
Hope this helps.
Rosada Bennett, Librarian
Federal Mine Safety and Health Review Commission
1730 K St., NW 6th Floor
Washington, DC 20006
(202) 653-5030 - fax