I found a stunning quote that backed up the information too....

Page 77 of Management Challenges in the 21^st Century by Peter Drucker

“Every book publisher knows that the bulk of its sales (some 60%) and practically all of its profits come from the “backlist,” that is, from titles that have been out more than a year or two.  But no book publisher puts resources into selling its backlist.  All the efforts are put into selling the new titles.  A major publishing firm had tried for years to get its salespeople to sell the backlist without any success; and it also did not itself spend a penny on promoting it.  Then one outside director asked: “Would we handle the backlist the way we do if we went into it now?” And when the answer was a unanimous “no,” she asked: “What do we do now?”  As a result the firm reorganized itself into two separate units: one buying, editing, promoting and selling the new titles published in the current year; one promoting and selling the backlist.  Within two years backlist sales had almost tripled-and the firm’s profits doubled.  

Here is what is REALLY INTERESTING...........

Recently, while reading the news on the Internet, I came across the following quotes from a news article published in the Minneapolis Star-Tribune.  Unfortunately, the article has been removed (over three weeks old) so I can't provide a direct link.  Sorry :(

"The next time you walk into a bookstore and buy a copy of some venerable classic -- "A Farewell to Arms," say, or "To Kill a Mockingbird" -- feel good about yourself. You're not just buying a book; you're keeping publishing, which has replaced theater as the fabulous invalid, as healthy as it can be.  That's because old books in new editions, not this week's bestsellers, are the profit engine that drives publishing."

"Backlist is easy money, and there can be a lot of it."  Robert Gottlieb, former editor in chief at Knopf as well as the New Yorker, said the profitability of the entire Knopf line depended on the Vintage/ Anchor line of paperbacks.  "They generated more profit than Knopf hardcover, Pantheon hardcover, etc.," he said. "A very strong backlist is more dependable than frontlist fiction, except from repeating genre writers who turn up dependably year after year. In my view, a healthy backlist provides up to 50 percent of a publisher's volume and with a lot less work" than new books."

Then, Mr. Gottlieb discussed some of the history behind the rise and fall of them in the publishing world.

"The method of maintaining a backlist has changed over the years. When company chief Alfred Knopf was alive, he would regularly publish authors that sold only a thousand or so copies, secure in the knowledge that he would move the rest of the books out of the warehouse at a gradual rate over five to 10 years.  But, in the mid-'70s, there was a change in the tax law, and books in the warehouse that publishers had previously been able to deduct as assets were now considered a liability. The result was that print runs became smaller and fewer esoteric books were published. Books were sold off as remainders within a year of publication, as opposed to being held in the warehouse."

"Over time, backlist disappeared," literary agent Fran Collin said. "Then, gradually, interest went up, and CEOs came in who weren't book people, and they said, 'There's money here.' And places like Doubleday, which had been around forever, and had long, long backlists, began to say, 'Hey, what an idea; let's do more of it.' And backlist, which had often been hardcovers, because the books were still in the warehouse, began to be almost completely a trade paperback business."

Finally, Gottlieb discussed some of the profit-related issues associated with backlists.  This is information  I didn't know, since I don't work in the industry and know all the nuances. 

"As long as a publisher keeps a book in print, the publisher can keep the book for the term of the copyright without paying any additional advances. But if a book goes out of print, the rights revert to the author, and he is free to make a deal with another publisher.  If a publisher does let the rights revert to the author, and that book has an unexpected afterlife, big money can come into play. Collin recently negotiated a seven-figure advance for a 10-year contract for that perennial young-adult novel of the American Revolution, "Johnny Tremain" -- double the amount paid for the previous license for the book.

There's no way a large-scale commercial publisher can be set up today without a viable backlist, Gottlieb believes. Despite the comparative success of such recent imprints as Talk/Miramax and Disney's Hyperion, "in the long run it won't work," he said.

"Overhead grows, you can have a bad year for bestsellers, the cost of acquiring the biggest writers escalates, etc.," he said. "Hyperion and Miramax will either have to develop a backlist or buy one." <--to me, this is excellent information

The backlist books that continue to sell are sometimes surprising, and sometimes not surprising -- classic 20th-century fiction and inspirational self-help.

"Our major backlist titles include 'The 7 Habits of Highly Effective People' -- a major, major backlist book," said Simon & Schuster's Adams. "For years, 'The Road Less Traveled' was huge. Over at Scribner's, Hemingway and Fitzgerald titles remain very strong -- they've never been out of print. Edith Wharton is quite strong. Thomas Wolfe is not so strong anymore. And do you know what still sells very well? 'How Green Was My Valley.' "