I'm only ignoring the long term because I'm looking for evidence that the rate at which the market produces new, timely works is reasonably close to what the demand for such works is.

Close enough for government work, I suppose:

"Conservative estimates are in the hundreds of thousands - if as few as 600 books have been stripped at each of the closing stores (600 X 182 = 109,200). And thousands of books have been stripped at each store before being shipped back to distribution centers for disposal." http://donatenotdumpster.blogspot.com/2010/01/despite-our-pleas-borders-has-trashed.html

Indeed, the publishing industry thinks nothing of pulping millions of unsold (or libelous) books each year. And there was no outcry in 2003 when 2.5 million romance novels from the publisher Mills & Boon were buried to form the noise-reducing foundation of a motorway extension in Manchester, England. http://www.nytimes.com/2007/03/04/books/review/Schott.t.html

Even the Library of Congress doesn't want to keep copies of everything:

The Library receives some 22,000 items each working day and adds approximately 10,000 items to the collections daily. http://www.loc.gov/about/facts.html