Do you even know what an overwhelming majority ninety percent is? According to the clearly un-biased ELSPA’s Intellectual Crime Unit (where’s the Law and Order spin-off for that one?), seeing someone playing DS without an R4 cartridge in the US is a rare site. I could spout some anecdotal evidence, but let’s look at numbers.

Assume that people who have the R4 never buy games and that they represent 90% of the market.

There have been roughly 20.67 million Nintendo DS consoles sold in America to date. Using the ELSPA estimate, only 2.67 million play legit carts.

There have been 6.54 million copies of Nintendogs sold in the US. Therefore, every legit user bought 2.44 copies of Nintendogs. With four versions of the game, I suppose that is theoretically possible, however extremely unlikely.
There have been 4.51 million copies of Pokemon Diamond/Pearl sold in the US. Therefore, every legit user bought 1.68 copies of Pokemon Pearl/Diamond. With two versions of the game, I suppose that is theoretically possible as well as long as the majority bought both copies of a ostensibly identical game.
There have been 3.95 million copies of New Super Mario Bros. sold in the US. Therefore, every legit user bought 1.48 copies of New Super Mario Bros... Huh?

As a DS developer, I am all about protecting IP. But when you lie about it, ELSPA, you weaken your stance as a group that can be trusted with providing developers and consumers any information whatsoever. I have no doubt that the R4 is causing people to pirate games rather than buy them, but we need to figure out (1) if this is really a problem and (2) how to deal with it in ways other than saying “seventy hojillion users are pirating games and no one is making money!”