I don't think its over 5% for the consoles. In terms of absolute figures, yes multi-console ownership has probably increased with price drops in the last year as a raw figure, but in terms of total console users I doubt the figure has budged much at all.
Frankly, its a massive drain of time and money. I don't think an average gamer spends more than $500 on gaming in a year, and its probably significantly less than that, just looking at my own purchases over the years.
My (read: my parents in years further back) spending on gaming goes something like:
1992 - Sonic 2, Genesis - $250
1993 - Sonic 1, Bubsy, Sonic Spinball - $150
1994: Sonic 3, F1 Racing - $80
1995: Game Boy, 3 games, Sonic & Knuckles ~ $250?
1996: N64 + Mario 64 + GB game - $390
1997: Two extra Controllers, Star Fox 64, Tetrisphere, Diddy Kong Racing, Mischeif Makers, Pilot Wings 64 , Mario Kart 64 - $400
1998: Yoshi's Story, Banjo Kazooie, Zelda 64, F Zero X, GB game - $275
1999: Dreamcast, Sonic Adventure, Donkey Kong 64, Super Smash Brothers - $420
2000: Mario Tennis, Star Wars Pod Racing, Legend of Zelda: Majora's Mask - $180
2001: Game Cube, Smash Brothers, Pikmin 3, Mario Party 3, Jet Grind Radio, three GC controllers - $450
2002: AC, Metroid Prime, Sonic 2, Super Monkey Ball, Mario Sunshine - $250
2003: Viewfitul Joe, Zelda GC, Soul Calibur 2, Prince of Persia, Ikaruga, F Zero GX, Beyond Good & Evil, Mario Kart, GBA SP, GBA games - $650
2004: DS Phat, Mario 64 DS, Tales, Viewtiful Joe 2, Pikmin 2 - $315
2005: Resident Evil 4, Killer 7, Sonic Rush, Advance Wars 1, Mario Kart DS - $205
2006: Wii, Zelda Wii, Rayman Wii, 3 Controllers, 3 nunchucks, AC DS, New Super Mario Brothers, Age of Empires DS, MLB Slugfest $605
2007: Galaxy, Fire Emblem, Batallion Wars 2, Paper Mario, Zack & Wiki, Metroid Prime 3, Star Fox Command - $335
2008: Layton, Advance Wars 2, Yoshi's Island DS, Civ Revolution DS, World Ends With You, Blast Works, Boom Blox, De Blob, Nights, Geometry Wars: Galaxies, Brawl, MLB Power Pros, Wario Land Wii - $510
2009: Fire Emblem DS, Wii Fit, Shaun White Snowboarding, Brain Training - $210 (and counting)
Just looking at my own history, $5,300 on gaming over ~18.3 years, suggests that $300/gamer/year is probably more than what a significant chunk of the audience spends based on attach rates for the GB, Genesis, N64, DC, GC, DS, and Wii. If thats the case, with each console effectively impossible to own for $300 in aggregate given attach rate averages (7, 7.5, and 8.3 for Wii/PS3/360) its very likely that only people with huge sums of money and huge amounts of time buy more than one machine and a number of games for each...
People are difficult to govern because they have too much knowledge.
When there are more laws, there are more criminals.
- Lao Tzu
