ICv2 is mainly a newsletter for retailers, but numbers guy Milton Greipp does a great service to the industry as a whole by tracking the sales numbers and trends for comics and graphic novels. His most recent set of results, revealed in a White Paper at C2E2, shows that manga sales were down 20% in 2009, after sliding 16% the year before, with the most recent drop coming mostly in the bookstore channel.
This weekend, a crack ICv2 team went out to document this trend by counting the number of volumes of Naruto stocked in the major chain bookstores in Madison, Wisconsin (where ICv2 is headquartered). Amazon, which carries all 47 volumes of the top-rated series, gets a score of 100%, which of course is hard for the bricks-and-mortar stores to match. Indeed, although Borders used to carry every volume of every series, the Madison store only had 29 volumes, or 62% of the series. Barnes and Noble did a bit better, with 39 volumes, or 83%. The article is worth reading in full because it puts these numbers in context.
Any statistician can tell you that a small sample size doesn't give a reliable result, but I believe these counts because they match my own experience as well as reported trends: Borders, in particular, has shrunk its graphic novel inventory. Using just one series has another limitation, though: In my experience, Borders has a wider range of titles available than B&N, which seems to carry a narrower range of manga overall.
In his White Paper presentation at C2E2, Greipp discussed a number of factors affecting bookstore sales of manga, including his own hypothesis that the shoujo manga fans have moved over to Twilight, and that shoujo readers tend to drop comics as they get older. It's also true that books like Naruto and Bleach no longer get the boost they once did from having the anime broadcast on Cartoon Network. With the anime version of Kekkaishi set to debut on Cartoon Network on May 29, it will be interesting to see if manga—and the bookstores—get their mojo working again.