"...The survey was conducted between 29 Nov and 2 Dec, and the number of respondents is 598.
"Do you think yourself as an Otaku?" and 20.4% said Yes, while 'No' takes up 51.1%
On the other hand, to the question "Do you feel stress?" Females who answered 'No, they don't think themselves as Otaku' said Yes (54.9%), they feel stress. But 'Otaku' females only accounted for 37.7%. Because pursuing a favourite thing, gives great satisfaction.
The things that these 'Otaku' females hanker after, are
1: Manga & Anime,
2: Pet,
3: Artiste,
4: Branded Goods
For Number 2, there's a new word called 'Pet Otaku' who are 'Females on the rise, who lavish their love on pet like a human/son'
Yahoo findings: 20.4% females claim as Otaku (in Japanese)
IMO the survey is too bias, because the number of respondents are too little to be hardly any representative of all the females in Japan. But in a way I'd agree that females with devotion into a particular activity, are on the rise. You'll realise more and more single females, and what can they do when they don't have boyfriend or friends to keep company? Well these activities can fill up that void in their life, and have some kind of satisfaction. But wow, spending on branded goods will need a lot of $$$