In one of the least surprising bits of publishing news out this week, the New York Times’ Alex Mindlin reports that children’s book sales in 2006 rose last year at a rate that disappointed the industry, according to a report released in June by the Book Industry Study Group. Granted, that’s just like saying the profit margin wasn’t as high as it should have been even though there was still money to be made, but no matter: sales rose 2.5% in 2006 and 9.4% in 2005. The difference? Well, you can guess.

And the Harry Potter effect demonstrates a truth about sales of children’s books: they are highly volatile and dependent on blockbusters. “It is unquestionably the most volatile sector, because it’s hit-driven,” said Albert N. Greco, a senior researcher at the nonprofit Institute for Publishing Research, who analyzed the data in the study. So it should follow that 2007 will see another major spike in sales, except that the industry is looking ahead and projecting much doom and gloom. Because, as Greco points out, “There’s real concern about who’s going to replace Rowling in juvenile numbers.”