The official NPD February 2008 thread

[Dolla Dolla]

krik said:

ioi, I just ask you to be "The Boss", treat NDP data like any other official source. Adjust VGC based on it, make your numbers reliable.

This is where you are assuming ioi is trying to be close to NPD.

It has been made clear that ioi is no longer adjusting data due to what NPD releases.

And here's a quote from another thread that sums up ioi's feelings towards the whole thing:

ioi said:

I do get annoyed when people compare our data to NPD and say "VG Chartz are miles out". That just shows a huge ignorance and lack of intelligence in looking at what the figures actually represent, where differences may come from and the fact that many of the "deviations" are totally "intentional" in that we are not trying to replicate NPD and are of no suprise to me. What many also don't understand is that NPD will make adjustments after they release their initial figures - which are not made public - and those who do see the adjustments will see that often it brings their inital data closer to ours.

ioi