I actually wouldn't be surprised if it was literally 0.
The thing about appealing to adults is that they have a lot of disposable income.
I bought my mum a DS and professor layton for her birthday, she was a stereotypical 'non gamer' before this gen. Within a week she had already bought 2 new games.
An adult will go out and get Wii Sports, Fit, PLay and WSR and think nothing of the cost. A child however has to save up for months to buy a PS3 or 360 and even a single game. Why do you think the Wii's attach rate is so high (keeping in mind that traditionally a high userbase = low attach rate, happened to the Nes, Snes, PS1 and PS2)







