Pareto's Principle says 80% of effects are brought about by only 20% of causes. It's a handy rule, and one the NPD Group are busting out to try and explain 2008's year in software sales.
See, over the last few years, video game sales have held true to Pareto's Principle. In that 20% of games have accounted for around 80% of sales. But in 2008, things were a little different, and they were a little different thanks to the Wii.
While PS3 and 360 sales still held to the 20/80 rule, the Wii didn't. Only 13% of Wii games accounted for around 80% of sales. NPD's Michael Klotz breaks it down even further, telling Gamasutra:
When you're looking at the Wii, what's really interesting is, when you look at 2008, the top ten SKUs accounted for 44 percent of the sales. There were 432 titles available in the market for the Wii... strictly retail.
You're looking at 422 titles that are competing for the remaining 56 percent of the sales.
So, yeah, what he means is, for all the shitty third-party ports and shovelware that hit the Wii in 2008, the only things that really sold were Nintendo's own Wii Fit, Wii Play, Mario Kart and Smash Bros. And combined, they sold a lot.