According to IGN and NPD, every Capcom-Wii game is overtracked

[dude17761991hatp]

Resident Evil 4 -- 759,000 units sold
Resident Evil: Umbrella Chronicles -- 398,800
Okami -- 165,900
Zack & Wiki -- 116,600

This information comes from a recent IGN article

http://wii.ign.com/articles/952/952652p1.html

What is the margin of error for NPD, and what is the average difference between the numbers VGChartz posts and what NPD reports?