…Last year I wrote about some very interesting research being done by Paul J. Heald at the University of Illinois, based on software that crawled Amazon for a random selection of books. At the time, his results were only preliminary, but they were nevertheless startling: There were as many books available from the 1910s as there were from the 2000s. The number of books from the 1850s was double the number available from the 1950s. Why? Copyright protections (which cover titles published in 1923 and after) had squashed the market for books from the middle of the 20th century, keeping those titles off shelves and out of the hands of the reading public.
Heald has now finalized his research and the picture, though more detailed, is largely the same: “Copyright correlates significantly with the disappearance of works rather than with their availability,” Heald writes. “Shortly after works are created and proprietized, they tend to disappear from public view only to reappear in significantly increased numbers when they fall into the public domain and lose their owners.”