Ah, back when I originally wrote this, I had never even heard of HAIKYUU!! before. That just looked more similar to a soccer ball. I hope some of my data was helpful in your research project.
Points I found interesting during my initial research. Manga is often stigmatized in the US as being sexually exploitative of women. Yet, manga has a far larger readership. ONE PIECE alone outsells every book Marvel publishes combined. We in the US have no idea just how many different manga series are running at any given time in Japan. We see the cliche of 'hentai', but that's only because those are the series that are brought over to the US.
Well, it's a smaller sample size, but I would think it wouldn't be too different from the bigger publishers. Oddly enough, you'd think the ratios would be more favorable with the larger readership.