Amazon has made some Nielsen Bookscan data available free to authors via their Author Central program. Authors who sign up for the free program can see geographic weekly sales data for their print books.
Amazon vice president Russ Grandinetti said, “Authors are an important community for us … We’re really happy to make it easy and free for them to see geographical BookScan data updated weekly, as well as historical Amazon bestsellers rank, for their books. We hope this creates an improved feedback loop for authors and enables them to develop more effective methods for reaching the widest possible audience.”
Bookscan compiles sales data from various sources — primarily chain bookstores — and tracks around 75% of book sales for most titles.