Nice, ioi! Keep up the good work!
Thanks. Remember that NPD figures themselves are only an estimate (from ~60% coverage) and that their figures shouldn't be taken as fact - although they are of course much closer than ours are likely to be.
If anyone takes the trouble to compare Famitsu and Media Create figures you will find a larger discrepancy between their figures (two large professional tracking agencies) than between our data and MC / Famitsu for Japan or our data and NPD for America.
I don't think that is bad going myself, especially when there are so many improvements to be made.
When DS and Wii sales calm down to more realistic levels and aren't dominated by sales spikes, shipments and so on then we will see our data get better and better again. We essentially applied the same extrapolation factor to DS and Wii from our raw data but as you can see one was too high and one too low and it is difficult without more coverage to account for anything like that.