Because of the strange distortions of copyright protection, there are twice as many newly published books available on Amazon from 1850 as there are from 1950.
The above chart shows a distribution of 2500 newly printed fiction books selected at random from Amazon's warehouses. What's so crazy is that there are just as many from the last decade as from the decade between 1910 and 1920. Why? Because beginning in 1923, most titles are copyrighted. Books from before 1923 tend to be in the public domain, and the result is that Amazon carries them -- lots of them. The chart comes from University of Illinois law professor Paul Heald. In a talk at the University of Canterbury in March 16, he explained how he made it and what it shows. He said:
This is super exciting, interesting preliminary data, I think. I had one of my students write a computer program that would crawl through Amazon.com and pull 2,500 fiction titles at random. ... The findings are absolutely fascinating.
We broke these out by decade. ... You would expect that if you can crawl through Amazon looking at only new books and only books sold by Amazon -- so these are not used books, these are not sold by Amazon associates, this is what's in Amazon's warehouses -- of course, the biggest number of books is from the decade 2000-2010. That's what you'd expect; they're more recent, more popular. Drops off really quickly for books in the 1990s, 1980s, 1970s, '60, 1950, 1940, 1930 -- here's the point in time where books start falling in the public domain. Suddenly it goes up and up and up. There's as many books [that] Amazon is selling brand new right now from the 1900s to 1910 as from the 2000s to 2010. You go all the way back to 1850 -- there's twice as many books from the 1850s being sold on Amazon right now as the 1950s. So this sort of confirms the notion that there's some sort of positive public-domain effect ...
Heald says that the numbers would be even more dramatic if you controlled for the number of books published in those years, because there are likely far more books published in 1950 than in 1850.
You can watch Heald's whole talk, "Do Bad Things Happen When Works Fall Into the Public Domain?" below. His comments on this chart start at about 12:40. Thanks to Yoni Appelbaum for the pointer.