An excellent new study at http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2290181 looks at a random sample of new books for sale on Amazon.com shows three times more books initially published in the 1850’s are for sale than new books from the 1950’s. Why? The paper presents new data on how copyright seems to make works disappear. First, a random sample of 2300 new books for sale on Amazon.com is analyzed along with a random sample of 2000 songs available on new DVD’s. Copyright status correlates highly with absence from the Amazon shelf.