I'm wondering if online sales may account for some of the discrepancy. Perhaps Wii's sell at a better pace online because once they get in stock, they sell out immediately. Since this is the first time NPD has accounted for online sales, that could explain the difference.

So they've been wrong twice in 6 months? 

Think you might be over-reacting a bit? 

Its true, right? Ultimately what the companies care about is how all their hardware sells. I think it also paints Sony in a pretty good light.

In $ terms, MS will always be behind the 8-ball because it has only a single console/handheld (that is still selling - Xbox/GC can be ignored).

Take out handhelds if you want... for NPD July/US:

Ninty: 400k (42%)

Sony: 370k (40%)

MS: 170k (18%)

...just numbers in the end :)

See, the problem is it's easy to spin these discrepencies as decent, just like vgchartz does every month.

But when Vgchartz is off 20% for any particular console, and it could be either direction, any given month, the numbers just dont have any real value over educated guessing, because the average layperson could make a educated guess that would be just as close. For example, for 360 sales, Vgchartz could be +- 20%, that's a 40% range, and just by some basic guessing and previous months weekly sales rates from NPD as a baseline, I bet I can get closer than that!

Back to a little discussion of the numbers, what really beat VGC and other predictors (Pachter, who might be basing a lot on Vgchartz) the past month was that 360 held steady. Most got the PS3 increase pretty close, helped by Sony's "double at major retailers" comments. But most predictors showed 360 falling a lot, apparantly assuming PS3 sales took away 360 sales, and that didn't happen. The second major deviation was, Wii sales higher than everybody expected, which are simply people inability to predict when Nintendo will send a big shipment through.

I don't want to get into a debate, so I will just say they have to start somewhere. I think it is pretty clear how much they have improved, and while the weekly numbers may not be the epitomy of accuracy as you said they are good enough for casual observations. But I have to ask what should ioi do in your opinion then? Should he not do the weekly #'s at all? I guess I am just wondering what you think should be changed?

 @Sharky, 

If you want to make a guess truly without data and just a guess you should make it now.  But in any case for your test to mean anything you would need to do this on a regular basis. Once proves nothing, month over month would prove something.  

Well it does appear as Source has mentioned that VGChartz estimates have improved. Not only has the average difference declined for the last 3 months as he mentioned but, as that would indicate, the individual differences are improving.

In May the site had 2 systems within 10% of NPD and 2 off by more than 30%.
In June it was 3 systems within 10% and 1 off by more than 30%.
Last month it improved to 4 systems within 10% and none off by 30%.

Not as valuable as per system sales but total system sales have improved markedly from being 7% off to 4% to spot on this month (not including GBA).  So if the site can keep getting the total number right then it's just a matter of getting the shares correct, admittedly the tougher and more important of the two.

Now the bad side.  Although average error improved last month a lot of it was due to the GBA moving from way off to almost exactly right.  Remove the GBA and and the average error was slightly worse (14.8% vs. 14.5% last month).  Also despite the improvement in average error the variance increased.  That's because the ones that were right were more right but the ones that were wrong were more wrong. 

The only systems VGChartz seems to have issues tracking are the DS and 360. Not counting the GBA they account for almost half of the average percentage error over the last 3 months (7.4% of the 15.4% average error). Which since there's only 6 systems that would of course mean those 2 typically have twice as much error as the other 4.

Anyways, so long as VGChartz doesn't backslide its doing a pretty good job for a free service in my book.

This is a great site. Very active community good job tracking sales and great admins. Without VG Chartz i would be trying to hack my way into NPD ;o. I would probably get cought and get my ass thrown in jail. Thank you VG Chartz for keeping me out of jail

Huh? PS3 below X360 in US? Close but not enough... (Almost) tie in US is a win for PS3 WW... Yeah... I've tried to cheer up.

So next NPD should be released Sep 11? Do I have that right? Or is it Sep 18?

The good thing about a week delay is we get next months numbers a week quicker, assuming they dont delay again. If Sep 11 is right, that's a fast turnaround. 

Thanks Erik, Thanks KruzeS! This needs to be pointed out.

But remembering the nasty E-Mails ioi received from NPD, I think it's not beyond those NPD guys to skew their numbers just enough to make VGChartz look bad. Over the years NPD have probably published almost as many corrections to their numbers as they have published original sales reports which gave me the impression that their own numbers are not sacred to them as they should be. Every month that VGChartz sticks around will put pressure on NPD to improve their quality.