I'm on my cellphone so it's not easy to look it up or copy it, but for an example check out one of the quotes in my third post in this thread:

http://www.vgchartz.com/forum/thread.php?id=17285

Can't say.  Unless you pay for the numbers you don't get the totals.

You can add up the months as they are released but then you miss all the backtracking, adjusting and correcting NPD does.

That's the problem with NPD. 

We've all noticed the descrepency.... These numbers are going to be off from time to time but there's no reason to bash this website.

The history of this site has been that if a console (eg, the PS3) has been under tracked, the numbers will be corrected.

There is no correct source of numbers except the numbers posted as shipments by the video game companies themselves. The NPD numbers are most likely the closest to correct, yes, and VGChartz is dealing with smaller sample sizes and seemingly has to rely a little more heavily on various components of its formula that make it a little less fluid in the case that sales swing heavily or make unexpected turns.

Let VGChartz work through its growing pains without being so negative. We all see that there was a problem -- almost everyone was surprised by the NPD's numbers.

@Jandre: The thing that basically causes VGC to be off, that it is off, is sudden changes in demand and therefore sales. Not that much in supply issues. In a normal time of a year with steady sales, VGC hits the spot, but (especially with) the lull after christmas, slight overtracking/undertracking is expected, which will be corrected when there's enough reasons for it. Patience.

NPD is wrong, VGC is wrong, we won't know until fiscals. Last fiscals proved VGC to be better for Wii.

Wait some time , ioi will proabbly update the numbers soon :)

Aww Claude left me a response! I guess you could refer to lunchtime as "meds", nothing calms the raging 12 year old boy inside me quite like a happy meal from McDonalds..

Right and me asking why there was a huge difference between the numbers means im whining? It was a question directed at people who wait every week and reference this site as fact. Im not complaining, I asked if it was going to be corrected, as the last NPD was not.

"OMG OMG OMG VGCHARTZ IS BIASED!!!" No, I didnt. It has been drastically wrong twice in a week, so I was tyring to see if anyone had an explanation. Also, with things like this happening no one would take this site seriously anymore. Thats something I think even ioi knows, and I defend this site all the time. So on the actual  site, I asked the regulars a question.

So some losers will come in and say things like "ARRRRRGH MAKE YOUR OWN SITE! ARRRRGH TAKE YOUR MEDS!! ARRRRRRGH YOUR TAKING TOO LONG TO RESPOND! IM GUNNA POST THIS PICTURE!!!"

Oh god shut up, lol. Do any of your crybaby angry guy posts ever have relevance? It was a question, with a tad bit of fanboyism. This whole site is for fun, lighten up Claude. Who knows, maybe upon removing that stick you can get that corner office job you've had your eye on for 15 years.

Just thought I would copy and paste Iois take on PS3 hardware in January NPD.

"PS3 figures also defy logic to an extent. Sure people will be buying more PS3s since there is a shortage of 360 premiums but still that is a big jump from the kind of sales we saw in November / Dec (relative - it is obviousy less but not as much less as you'd expect given the modest holiday sales). Again, our data consistently had PS3 at the bottom of the pack, despite 360 shortages and I find it hard to see how we could be 80-90k too low unless some chains were seeing an enormous PS3 boost - all our data had it selling on par or slightly less than this time last year."

Taken from the January NPD thread.