According to The Research Institute for Publications (RIP), the yearly sales of manga (magazines and comic books) in 2009 was 418.7 billion yen and made a year-on-year decrease of 6.6%, which is the largest drop since the onset of RIP records.
Chart: Manga Sales in Japan 1991 - 2009
Manga Magazines: 191.3 billion yen (-9.4%)
Comic Books: 227.4 billion yen (-4.2%)
RIP attributes the drop to three reasons:
1. Effect of the economic recession
2. Spread of Manga Cafe
3. Small number of big hit titles